Vertical Milling in the Home Workshop

ARNe -_3 THROP

VERTI MLLING IN THE ME 0 K OP

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Argus Books Argus House Bounda ry W ay Hemel Hempstead Hertfordshire HP 2 7ST Eng la nd

CONTENTS Chapter One

EVOLUTION OF THE VERTICAL MILLER 12 Early history of indu strial m achines: milling in th e early sma ll lath es : mi lling attachmen ts for lat hes ci rca 19 20s: E.T, W estbu ry's experimental machine 1964: the Dar e-Westbury m achine 1968: cu rre ntly avail able sma ll machi nes and attach ments,

Chapt er Tw o

MILLING FLAT SURFACES 27 Surf aces paralle l to table: simple fixed-radius f1 ycutt ers: var iab le-radius bor ing head flyc utting: multiple -tooth face m ills: work hol ding: m ult ip le­ pass mi lling: surfaces square w it h table : using side of end mill.

Chapter Th ree

SLITTING AND CUTTING 35 Use of slitting saw for cutting through machinery component bosses : eccentric sheaves and straps : mar ine type big ends of connecting rods.

Chap te r Four

KEYWAY CUTTING 37 Endm ill ing round ended 'feath er' keyways : keyways on taper shafts : use of disc tvoe cutters for plain sunken keyways : \Noo dru ff keyways: making Woodruff cutters in the home workshop : table of suggested sizes of \N oodruff keys and kevv vavs fo r model engineers,

Chapter Fiv e

FLUTING COMPONENTS OTHER THAN TOOLS 43 Correct form of flutes ir loco connecting and cou pling rod s: mounting rods against anglepla te for flu ti ng : parallel flutes: taper flutes: preferred type of cutting too l.

First pub lished 1977 Second im pression 1979 Sec ond edi ti o n 1984 Rep rin ted 1986, 1988 , 1989, 1990, 1991 . 1993

© A rg u s Bo o ks Ltd

1977

All r ights reserved . No p art of this publication m ay be repro d uced in any f o rm by print. photography, microfilm or any othe r mean s wi thout written permission from th e pub lisher. ­

ISB N 0 852 42 843

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Ph o t ot y p esetti n g by Perf o rm an ce T y pesetting, Milton Key n es Print ed and bound i n G reat Br it ai n by Biddies Ltd . Guil d f o rd and K in g 's Lynn

Chapte r Six

BORING 45 Dealing with parts too large to swing in lathe: trepanning large ho les.

Chapter Seven

'J I G- BORIN G' 46 Using the miller as a measuring machine : drilling ho les at one setting of work and precise cent res: eng ine be am: b ack-lash pr ecaution s: tri p gea r com ­ pon ent : mu lti-ho le boiler plates.

Chapter Eight

DIVI DING HEADS AND TOO L MAK ING 66 Fluting taps : example 5-flute Acme tap : producing a small fine too th milling cutter w ith ball end : use of table stop blocks: combination of rotary tabl e with ma in table movement: large 60 deg ree coun­ te rsink fluting .

Chapter Thirt een

DIVIDING HEADS AND GRAD UATED SCALES 71 Cutti ng graduation marks : use of rotary 'engr avi ng' cutters : use of no n-r otating plani ng t ype tools : use o f table stops to contro l line lengths : graduating cyli ndr ica l scales: gradua ting flat angular scales : checking correct way of figuring when stamping scales ,

Chapter Fourt een

CUTTER SPE EDS FOR VERTICAL MILLERS 74 Speeds affect ti me occupied on job: speeds too high may cause excessive cutter wear and chatter : rigi di ty of work, cutter and mac hine inferior as a rule to i ndu st rial condi tions, dry cutting inst ead of lubricated : Tabl e III gives speeds for cutters in different kinds of tas ks : m achi ne speeds may no t alwa ys be suitable .

Chapter Fifteen

WORK -HOLDING WITH D IFFICULT SHAPES 78 Comparison with full scale engi neering : use of chucki ng pieces on components : thin components and use of ad hesives : advisability of making fixtures fo r difficul t pieces : three -s ided angleplates.

Chapter Sixteen

CHUCKS FOR MILLING CUTTERS 81 Never use taper shank tools or chucks without drawbar: chucks for screw ed shank self -tightening collets : Clarkson chuck : Dsborn Titanic chuck: Chucks for tee -headed locking cutters: Clare chucks : use of small end mills and D-bits withou t locking features : ph ilosophy of 't hrow - aw ay ' cutters.

PROFILING 49 Curves on parts too large for lathe: loco frames : smokebox castings : machine pad bolts: loco con ­ nec ting rod s and coupling rod s.

Chapter Nin e

END-ROUNDING 52 Use of hardened f ilin g gu ides deprecated: mou nting work on rot ary table: sta nd ard size guide plugs: anti-slip precau tio ns: direction of feed for exte rnal and i nte rnal surfaces.

Chap te r Ten

DIVIDING HEADS 54 Simple ungeared div iding heads : using change w hee ls as index plat es: examples o f d ividing w or k : h exagons. squares. dog clutch teeth : avoiding odd numbers : the Myford w orm -geared dividing head : avoiding back-lash erro rs : packing block for bringing to lathe centre height: universa l steady stand fo r Myfo rd head: three further dividing heads.

Chapter Eleven

Chapt er Tw elve

DIVIDING HEA DS AND GE AR- C UTT IN G 62 Limitations to strai ght spu r gears : sim ple head : M yford worm -geared head: tooth cutting on integral pi nion : use of home made Ilvcut ters: Brown & Sharpe disc type cutters : selectio n of cutter to suit numb er of teet h : cutting a large coa rse tooth gea r: anti-slip back-up de vices ,

List of Illustrations Fig .

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 4 25 26 27 28

Ab w oo d mi llin g attac hme nt of the 19 2 0 s

E. T. W estb ury 's m ill ing m achine Dore-W estbu ry m achine Dare-W estbury M k II machine Rodney attachm ent Rodney m ach in e Am o lco attach men t A mol co m achine M ent or mach in e M aximat attach me n t Astr a m ach ine Tw in machi ne Senior m achin e Set of three fl ycu tt ers Flycu tt ing a bracket Flycutti ng connecting rod ends Flycutti ng t apered bar mat eria l Flycutting cy linde r soleplat e Facem il l M illing flywheel joint face Mi ll ing crosshe ad slide M illing bear ing jaw s in bedpl at e Slitting boss of ca sting Milli ng feath er kevw av M illing feath er keyw ay on tap ered shaft Mil ling keyway wi th slitting saw Se t of four Woodruff keyway cutters M ill ing W oodruff k evwav

13

14

15

16

17

18

19

20

2 1

23

2

22

26

2 8

28

29

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30

3

31

32

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35

3 7

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39

4 1

29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

Fluti ng loc omo tive co nnect ing rod Draw ing of stea m hook (lever) Phot ograph of st eam hook Profilin g pad bo lt Profiling coupling rods End-rounding wi th rotary tabl e Cutti ng t eeth in do g clutch par t Draw ing of st eady stand for Myfo rd div id ing head St eady in use on a gear cutti ng opera tic Thro p divid ing head Th om as versat ile divid ing head Kib bey/M .E.S. dividl nq head Clos e-up of flycut ter and pi nio n Gearcu tt ing w ith Brow n & Sharpe cutter Fly cutt ing 10 d .p, gearwh eel. front view Fly cu tt ing 10 d.p. gearw hee l. rear view Flut ing A cm e thread tap Cutt ing teeth of ba ll-end cu tt er Close- up of ball-end cu tte r Gashin g flutes in large count ersinking tool Rear v iew showing stead y stand in use Cyli nd rical m achine compone nt being grad uated Close -up of prev ious ope rat ion Graduating part -ci rcul ar arcua t e scal e on fl at surfa ce Tape -he ld w orkpiece bein g flyc ut Hern inpwav three-side d anglep late Tw o of the th ree sizes of Herninqwav ang leplates Clare mi ll ing chu ck Clark son mi ll ing chu ck Osborn mill i ng chuc k

4 4

4 7

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50

50

53

5 5

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58

5 8

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60

63

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6 5

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Preface In th e eng ineering in dustry the vert ic al miller is very widel y used . no t o nly for batch product lorrbu t also for tool ma king and the 'one -off' jobs whi ch are so common in general eng inee ring. In the home worksho p. w her e most job s are 'one-o ff' th e ve rsatility of th e machi ne makes it an i m port ant comp anion to the lathe. Thi s book des crib es many of the infinitely wid e range o f op er ation s wh ich can be done. and all those described are illustrated by photographs so that under­ st anding of th e methods is assured . These cove r work on part s of model loco mot ives. stationary engines machi nery . cutting too ls. gea rs, clutches, etc. Full informat ion is given o n the machine accessories wh ich are requi red, suc h as var ious types of cu tters and t he chuck s needed for t heir mounting on the m achi ne spind le. The use of chea p hom e- m ad e cutt ers i s shown and encouraged. Guidance is also give n on th e work- holding dev ices such as clamps. packings, vices. angle plates, dividing heads. rot ary table s, and w hich of thes e are needed for part icular kinds of w ork .

CHAPT ER 1

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Evolution of the Vertical Miller Th e horizontal mi lli ng machine evo lved natura lly fr om the lathe in t he fi rst or seco nd decade of t he nine tee nt h century. Eli W hitney (U.S.A.) is said t o have had one in use about 18 18 . and in Tools for the Job the lat e LTC . Rolt reco unt ed how the yo ung engineer J ames Nasm yth {later to become famous as the inventor of the stea m ham mer and ot her app liances l fixed one up and m illed the fla ts on hundreds of tiny hexagon nuts for a model of a Mauds lay marine eng ine. w hile working fo r Henry Ma uds lay . Draw ings of the ear ly hori zont al mill ers show suc h a resemb lance to t he la th es of that period that almost certai nly they were in fact lat hes w hich had been adapt ed to mil ling. The cutters we re really files. made by the fi le m akers of the tim es, using t he 'hand­ cu tt ing ' methods (really a hamm er and a spec ia l chisel) w hic h we re the only practice available at that tim e. The evolution o f the ve rti ca l m iller came nat ural ly afte r t he ho rizo nt al m achi ne. I have not found any reliable refe rence to a date by w hic h the vert ical m iller h ad appeared in industry , thoug h this m ust have been we ll before 190 0 . W he n model eng ineering sta rted to beco m e an esta bl ished hobby at the t urn of th e century quite a variety o f sma ll 12

lath es we re provided by di fferent makers. and the great ver satili ty of th e lathe created in it self a te ndency to make the lathe do every opera tion that arose . This wa s enhan ced by th e fact th at ma ny modellers were working men with very litt le cash to spend o n their hobby. Many we re the inge nious attachment s devised to enable the lat he to carry out work it had never been intended to do . Such makers as Drum m ond Brothe rs modified their lathes wit h tee-slott ed boring tables to help in this work . and even bro ught out t he famous ro und - bed lat he. wh ic h although int ended for a cut -price market. also had bu ilt into it the abi lity to do a lot more than just simple turning . But as the years wen t by it became ever more appa rent somet hing better was needed f or mi lling operations . No ne of the small mille rs produced by the mac hine tool industry we re oriented towards the home w orkshop, T hen in the 1920s the Abwcod Tool and Engi neeri ng Co. produced an exce l­ lent vertical mi lling at tachmen t fo r mounting on smal l lathes. especia lly the in. flat bed Drum m ond . though popula r adjustable features made it applicable to othe r lat hes too . It had a No. 1 Morse tape r arbor which fitted in to the lathe

3t

j:ig . t Abv/ood milling attachment of the 19205

13

spindl e. and bevel gear s with keywa yed shafts took the drive up to the vert ica l cutt er spind le. w hic h had a No. 1 M orse inte rna l taper. A ll the gears w ere equa l rat io m it re beve ls. so the cutter ro t at ed at t he sam e speed as th e lat he spi ndle . and all t he six speeds of the lathe were usable. The w or k wa s mounte d on the lathe bo ring table. and po wer feeding in one direction ca me from the lathe screwcut­ t ing gear. A phot ograph of this uni t set up on a Myford Super 7 is show n in Fig. 1. It wa s unfort una tely a low -vol um e. labou r int ensive uni t w it h vee slides needing hand scrapi ng . but w as selling in 19 30 for 7 guin eas. about a quar ter of the cost of

the Dru mmo nd lat he. A lt ho ugh o ut of producti on for ma ny year s now . it was in its time a co urage ous effo rt . but be lo nge d to the age w hen most home lathes were driven by fla t belt fro m a tread le or cou n­ tars haft. and the cost of electric mot ors made th e in d ep enden t m o to r drive uneconom ic in ho m e hobb y appli cati ons. Bu t th e need for a handy vertica l m illi ng ma chine had been recogn ised. and in the ear ly 19 6 0s that very good friend of model engineers. Edgar T. W est bury . com plete d an ex pe r im en ta l m ac hi ne. wh ich he desc ribed w it h drawings and pho t og rap h s in t he Model Eng ineer during 19 6 4 . T hat too wa s a very labou r

ig, 3 D ore- W est bury machine

Fig. 2 E.T. Westbury 's milling machine

14

inte nsive machine w ith vee slides, and the main castings w ere m uch t oo big to b e machi ned in th e ave rage ho me workshop. A t that ti m e he w as una ble to find any engi neering fir m wi lli ng to take it over and manu facture it. or ev en to do th e machin­ ing on a contract basis at such a price as it was thought m odel engi neers would be wl llinq to p ay. T hree years later I found myself with the opportunity to tak e a fresh loo k at th is desig n, whi ch he had di scussed w ith me during the experim ent al pe riod . I evolved a new set of d rawi ngs for a sim ilar machi ne, but using flat slideways more economically constructed. a reducti on gear f or low er bottom speeds , hollow spindl e for a draw bar. and othe r changes

int ended to make econom ies or im prove the pe rformance . This new design was discussed w ith Edgar. w ho agreed to the use of the name 'Dore-Wes tburv ' , the machi ne to be sold as a kit of sem i­ fi nished compone nts by my existing fir m Dore Engi nee ring, I was abl e to pla ce th e m achi ning o f the compo nen ts w ith a number of firms al read y kno w n to me . and the fi rst sets of mat erials began to go ou t to custo mers early in 1968. Si nce that t im e m any hundreds o f sets have bee n distributed . all over the wo rld . and are still be ing made in ever grea te r quant iti es by M o d e l En g i n e e r i n g S er v i c e s . o f Chest erfield . w ho too k it over from me in 19 7 1, w he n I wa nted , on acco unt o f age , to red uce m y comm it men ts , Castin gs to the origi na l design are, howeve r, st ill available fro m Waking Pre­ c is io n M od els o f 16 Dovecot Park . A berdour. Fife. Scotland KY3 OTA . and a machine fro m these is sho w n in Fig. 2. The Da re-W estbu ry mac hi ne is depicted in Fig. 3 and the sim ila rity be twee n the m wi ll be at onc e appa ren t. Du ring it s entire life the Dar e-Westbury has been un dergoi ng sma ll im provement s. and th e present supplie rs have now dec ided that t h e m o d i f i c a t i o n s a re s u ff ic ie n t ly st abilised for the presen t ve rsion t o be titled the M ark II model. From now on all ma chines supplied w ill be of this form . though st ill subject to certain op tional vari ations which custome rs w ill be able to select as t hey wi sh. T he more importan t chang es incl ude an in crease in t he quill travel from 2i in. to 4-1- in . Ext ra pull ey ste ps with a new ty pe of be lt extend the speed rang e sligh tly fro m 32 to 1880 r.p.m. w ith more int er­ m ediat es. provid ing for boring head fl y­ cutting on large radii right th ro ugh t o keyw ay cu tt ing with 1/ 16 in. cutters. The reduction gear system now fi tt ed has helical gears w hich run in an oil-bath.

15

Fig. 6 Rodne y ma chine

sealed against leakage even w hen incli ned away from the vertical, and is Quieter th an former ly. A large r table , 20 in. by 6 in., can be had as an optiona l al terna tive to the in. The co lum n and norm al 16 in. by cros s tube are steel. as always, but now t in. thick and eno rmously st iff. in. diamete r m icro m et er d ials are now

5t

standa rd. Th e down-feed w orm has for conveni ence been transferred to the right hand side of the head, a coa rser pitch rack is now used . and ther e are a numbe r of oth er m ino r im provements.

2t

18

Opposite, Fig. 7 Amolco atta chm ent 19

Although co lleg es and commercial workshops wil l probably wish to use the all -over be lt guard, it may be d eba ta ble if th e co st of this is justified fo r the so lit ary mat ure m ode l le r alo ne i n hi s home workshop. An alternative belt gua rd wh ich covers t he spi nd le pulley only and do es not im pede belt chang ing so mu ch is ava ilable and is shown on the M ark II machine in Fig. 4 .

No do ubt the most importan t i m pro ve­ ment is the (optional) provision of po w er feed fo r the lo ng movement of the table. A small m ot o r wit h a 4-step pul ley and enc lose d w o rm reduction gear provides feed rates of .5 . .62 . .85 and 1.1 inches pe r mi nute. A num ber of attachm ents similar in general concept , though much different in de ta il. to t he old Abwood . have com e on

<, Fig .

9 Menror machine, now superseded by th e

FB2 and Maximal attachment

the rn a rk e t in recent year s . Tew M achlnerv produce t he .Rod ney' to su it th e Mvfo rd M L7 and Super 7 lat hes. and :hi s is marketed by Myfords . It is shown in Fig. 5 and t he complete vertica l m ill er ba sed on t his atta chme nt is th at shown i n Fig. 6 . A not her attachment, t he 'A m o lco is supp lied by N. M ole & Co. Ltd . and appears in Fig. 7 This has it s ow n motor and attaches to t he top of t he lath e bed also. It is made as a compl ete ma chi ne. snown in Fig. 8.

Fig. 8 A mateo machine

20

Fig. , t A stra machin e

21

Fig. 12 Twin machine

Elliot m achine Equipment supp lied a continental mac hi ne, th e ' M entor' wh ich was available bo th in b ench and floor m ounted forms . Th e bench m achine is shown in Fig. 9. They also have the 'M axim al' attach ment to suit the lat he of the same nam e, whi ch fit s on the back of the lath e bed and has independen t m otor drive (Fig, 10 ). This is also avai lable as a floo r m achi ne, the FB2 . Ot her co m plete m achin es inclu de the 'Astra' suppli ed by Scot Urq uhart, w hic h is really a horizont al m iller w it h an ext ra ver tical spindle with it s own mo tor . Made in several sizes, the smal l one is sho w n in Fig. 11. Twi n Engin eering Co. introduced a bench ma chine illus trated in Fig. 12 and also a floo r m ounted machi ne of sim ilar size but slig htly di ff erent desi gn. Fina lly the old established firm o f Tom Senior Ltd . now produce their type E

mach ine w hich is floor mounted and shown in Fig, 13. So it will be seen that there are now many machines and attachme nt s which are of suit ab le dimensions for inclusion in t h e l i m it ed sp a c e o f m o s t home w ork shop s. It would be useless to give any deta ils of prices in a book of this kin d , as such info rmation would probably be incorrect by t he ti me the boo k was printed, and readers are therefor e recom ­ mended t o enquire of th e various adve r­ tisers. A summ ary of the leading particulars of all these m achines etc. is given in Tab le 1 but again specificat ions are ame nded by m akers as t im e goes by, and it can be no m ore tha n a general guide . A brief w o rd m ust be said about fore ign mac hin es. part icularly those coming from Far Eastern countries. I t wo uld appear th ere are several facto ries producing mac hine tool s and acce ssories. Some app ear to be quite good , bu t others are definitely not good, and I do hav e personal exp erie nce o f some of th ese. I have not had the chance to see one of the mill ing ma chines work ing, but those I have inspect ed i n exh ibi tions have some che ap and nasty feat ur es, although the mai n item s suc h as spind les, bear ings , and slideways m ay be excellen t. Some of t he machines are more suitable for com ­ merci al fact orie s th an home workshops but th ere ar e o thers of mo dest dimen­ sions. To anyone contemplat ing buying on e of th ese on e ca n on ly suggest that a close inspect ion shou ld be made by a kno w ledg eab le engineer , and that a wo rking demon str at ion should be requested , of th e actua l machine which is to be bough t. Fig. 10 Maximar ettscbrnent

22

23

'Rodney'

'Amolco

'Twin ' bench machine and floor machine.

'Seni o r type E' lIoor m achine. To m Senior. Ltd ., A tl as W or ks. Hig hto wn Heights. Liversedg e. W est Yor ks.

head.

'A str a' bench anrt floor Il1sch in()l'; Hor. with v ert .

floor machine

attach me nt nr

' M ento r rtlHch il1p. B.1nch an d f loo r. FS2 M axim at

M ll ch in e or atta ch m en t

Oench m iller.

i:t1l8 <:l lII Ulfl l.

T wi ll en!'!. Co. eelxton Way. Ho ly we ll i nd . Est . W atf or u. Harts.

Scot Urquhart Ltd .. 3 17. 3 /:~,1 , Earl sfield Rn .. Earl sfie ld . l ondo n SW18 300

F.'1,Jipm ent. U.LC. HnllHH, ViClu ,iH Hrl , London . NW 10 6NY

Cllio lt M nc:hlne

Ma klllH supp lter

I ABI F 1 (continued)

N. Mule & Cu. Ltd. 5. Tulp il s I line. WH l t",d . HHrtS.

' Rodney plus' floor rnachinc.

a tta chm ent.

Swive l head .

Swivel head

2MT plus M yfo rd thread 2MT

3 80, 640. 1 10 0 . 19 0 0 . 31 0 0 480. 9 50 . 16 4 0, 2 7 6 0

20 x 6

25 x 4t

M o tori sed head .

Swivelli ng haad

Rigid head .

2M T

2 MT

2 M T plus M yf or d thread

62 0 .90 0 . 12 0 0 . 18 50

120-2000 (six)

52 0 . seo. 165 0 .2 8 80 20 x 6

13 x 4~

24t x 6

Swive ll ing head. 2MT

3 50 ,640 . 7 80 . 20t x{

14 50

Comments

Rigid hea d .

Rigid head .

Rigid head .

Rigid head.

Spindle no se

2 M Tpi ll s M yf or d t hread

2 MT pl us Myfurd thread

M yf o rd th read

2 M T p lu~

2 M T plus M yford thread

Comp lete ki t o f parts. A ll machining do ne that wo ul d be d ifficu lt in ho m e w o rk shop. Head sw ive ls.

Sp indle spe eds

Mutur d riv e. 4 speeds, 325 to 16 0 0 325 -1 600

32 0, 450, 61 0 , 8 50.1040,1 490, 2 19 0 . 2 750

Dri ven from lathe sp in dl e

2 M T plus M y ford thread

2 M l pl us M y fo rd thread

Now superseded by Mk. 11

2 M Tp1 1l~

M yforn th read

Commen ts Un- machined castings only supplied Head sw ivels.

Spindle nose

T able sizt!

Fo r Myfurd & Ao xfor d tat hes. 15 x 6

For My/o rd M L7 anrt 57 7 lat hes. 15 x 4±

3 2 - 18 8 0

Tew M aChin ery ltd . M an o r W o rks Church SI. Cogg cnh o c, Northampton.

6. Ken net Vale, Broc kwel l. Ches lJou1ie lrt. 16 x 5 t (20 x 6 op tio n ]

3 4~ .90 . 188 304 . 7 9 0 . 16 50

16 x 5 ~

' Do ra Wp. ~tb llry· bench m ach ine kit uf parts Do re W est bury Mk.l l bench machi ne kit of parts.

S ervices .

M ode l !'ngin eering

Sp indle speeds 6 50 . 11 2 0. 18 50. 31 50

14 x 6

Tab le si ze

W estbury' bench mach ine kit of parts.

Machine o r attachment

Woking Preci sio n M on els Co. Ltd . 16 Doveco t Park Ab srdou r. Fifp.. Scot land

Make or supplier

TABLE 1

CHA PT ER 2

Milling Flat Surfaces

Of all m et al-w o rking operations the production of true flat surf aces is perhaps one of the mo st di fficult if rel iance has to be placed on han d t oo ls and ha nd methods. for it depends jus t abo ut com­ pl et ely on the persona l sk i ll o f the workm an. But a poi nt offse t from the spi nd le c en t re of a ve rt ica l mill ing machine must when rotated describe a fla t plane in space if there is no axia l movement. Therefore . provided the spind le is truly square to the tab le. an offset cuttin g t ool must generate a flat surface o n a w ork- piece att ached to the tabl e. Model engineering , just th e same as full size eng ineering. demands th e produc­ tion of a great many flat surfaces. so the ability of the machine to perform th is task in a simple way, without expensive tooling , is extremely important to the home work er.

Fig. 13 Senior machine

26

FlYC UTTERS The cheapest tool for the purpose is th e flycutter. usua ltv consisting of a small toolbit set in some kind of holder. There are co mmercially made ho lders avai lable. but i t is quite easy to make satisfactory holders at home. and they serve jus t as well Three ho me- made flycutters are

shown in Fig. 14. Each is jus t a Morse tape r arbo r w ith an enlarged head having a sla nti ng hole dr ille d in it to take a cutt er bit (t in . in these samples) wit h a screw to lock it in pl ace. The head d iameters are 1 t in.. q . in. and 2t in. so th e face s that can b e mac hin ed at one pass are roughly tin. to 1- in . wider in each cas e. They w ere m ade by bo ring through short pieces of st eel of these sizes to suit th e parallel parts of M or se taper arbor s. It is not pe rhap s wid ely enough known that tool merch ants can. if th ey will , supply M orse taper arbors of this ki nd. w hich are a st ock pr oduct of the large dri ll m akers. This m et hod of fabricating flycutt ers by using a ready made arbor wi th a head Loct ited on saves a good deal of time and some heavy st eel. The effectiveness of to ols made in this way is beyond question . Fig. 15 shows a brack et cl amp ed aga inst a large anglepl ate and being milled with on e. Fig. 16 shows one workin g on a steel connecti ng rod which has to be red uced from a circular section at each end. The rod is about 9 in. lon g. so it is held in tw o vices at the same time. and each end is taken down t o fin ished size b efore it is tumed over. Packings are used . diffe rent at each end to ensure the finished -surface is above the vice jaws, to avoid cutting

27

Fig. ' 4 Set of three flycutters

int o them , and the se pa ck ings en sure the ro d is at t he ri gh t att itu de fo r keep in g t he mi l led surf aces pa ra l le l to the ax is ,

Ow ning tw o vi ces ali ke m ay at fi rst t ho ugh t see m somet hi ng of a luxu ry , bu t as so on as lon g art icles have to be deal t

Fig. '5 Fly cu tt ing a brack et

28

Fig . 16 Flycutting connecting rod ends

with the benefit s ar e at once apparen t. Ano t her flyc u ttin g operation is shown in Fig . 17 wh ere a steel ba r is be ing

reduced t o a t apered sec tio n t o cu t up into wedge blo cks for co nnec t in g ro ds or the type in th e pr evio us picture. Thes e wedge

Fig. 17 Flycutting tapered bar material

29

Fig. 19 Facem ill

Fig. 18 Fl ycu tt ing cylinder soleplate

ground off to th e same pro jec tio n. and sharpened to a diameter of approx. in. In Fig. 2 0 it is shown mill ing th e face o f a half -flyw hee l iro n cast ing for a mo del

2t

bloc ks are needed for adjusting the beari ngs in the rod ends . The rec ta ngular sect io n bar is held in a vice on a tilti n ang le-p late whi ch has b een set at 6 de grees to th e table of th e mil ler with a St ar rett com bin atio n p ro trac to r. Th e ta pe red form w il l be seen on th e end of t h e c o m p l e t ed piec e l y in g on th e anglep lat e. This is an easy w ay of getti ng a speci al section which cannot be bo ug ht, and wh ich would, to say the least. be tediou s to make by filing. Th ese flycutt er hol ders do not allo w m uch adjust me nt of the radius of the cutte r bit, but w it h some ma kes o f bo ring head there is quite a lo t of adjust me nt . For exam ple the Dare boring head pe rmits of usi ng a cu tt er in a f i n, dia m . ba r at any in., and by sett ing th e rad ius up to saddle in or out on the slide body the radius can be adjusted by fine amo unts to suit any jo b w ithin the range. Fig. 18 shows an old type, pre-wa r bo ring head

2t

30

be ing used to face a cy linde r sole-p late fo r a slide valve engine mode l of in. stroke.

2t

st ationary engi ne. The casting is suppor ­ ted by a spec ial angle plate typ e of fixture, th e patte rn for w hich w as m ade in an ho ur. W ithout this fixture th e ope ration

FACE MILLS Of cou rse, mu lt i-cutt ing-edge face mi lls perm it mac hinin g a surface quicke r tha n a singl e point t ool can do, and with less snat ch and jerki ng, but co m mercia lly m ade they are very expens ive , and in the hom e workshop th e greate r productivity is no t usuall y of m uch conseq uence. Never­ thel ess, for anybod y w ill ing to spend the tim e needed th ey can be made in the ho me w orkshop , w ith several cutte r bi ts mounted in o ne m ild steel body . Fig. 19 show s a face m ill of t his kind , which was m ade originall y to screw on the spind le of a M yf ord lat he to do some repetitive mi llin g of a fa irly heavy nature , now no longe r required, but it is sti ll a good general pu rpose too l. It has 12 tool bits :l­ in. di am . set into flat bottomed holes, all 31

Fig . 2 ' Milling crosshead slide

wo u ld be so me w ha t diffic u lt. If th par alle l passes w it h an end mi ll m uc h cas ting w as held in a vice on the t able the narrower th an the face requ ired . Apar t point of cutting would be a long way fro m fro m taki ng mor e time th an a too l w ith a th e ho ld ing point. and mo vem en t o f th e wid e sweep. m inut e ridges te nd to be left casting under the pressu re o f cu tti ng w here the passes overlap. and these m ay wou ld be no t easy to prevent. Vibra tio n have to be removed lat er by filin g or and chat ter w ou ld be more likely. It very scrapin g. So w hile this meth od is feasible ofte n happens that the only wa y to ge t a the flyc utter or bo ring head is be tte r satis fac to ry jo b is to make som e equip ­ w he re the re is room to use it, and the ment specia lly for it. This is no t usuall y cutter bits are cheape r than endm ill s and wasteful. especia ll y jf a d uplic ate co m po­ easily sharpened like any lat he too l. nent is ever requi red. bu t t he equipme nt is However. an example of work wh ere a usually found adaptable for some o ther sma ll Cutte r and successive pas ses mus t job later. Doing met al cutti ng by 'knife­ be used is shown in Fig. 2 1 w here a flat and-fork' method s can Soon lead to bedplat e sli de for th e crosshead on a disaste r. The other half of the w heel mo de l sta t ion ary engi ne is be ing m illed. cast ing. wit h th e cast- in teeth for the The surfa ce being cut is in a recess tin. barring 'rack', can be seen in the bo tt om deep and the Corners canno t be dea lt w it h half of th e picture. The w heel is 9f in. by a to ol cutting the full Width. as the diamete r and has 96 teet h. radius left wou ld be too great. Not e th e Broad flat surfaces can be. and some­ stop ba r bo lted to th e table. Accura tely ti me s have to be, produ ced by Success ive squared w ith the ta bl e it provides not only

correc t location for the casti ng (wh ich was follo w ed by others) but also insurance against slipp ing . In the fu ll sized engi nes these slides we re always planed , and every eng ine­ build ing shop had planers for thi s ki nd of wo rk. In the one wh ere I w ork ed there we re seve ral of diHere nt sizes. and the arqest, built by Joshua Buckt on of Leeds. auld plane any cast ing up to 20 ft. long. 12 ft. wide and 12 ft. high . It w as said at tha t time to be the largest in Yorksh ire . and ce rtainly it often did castings for o ther firms. Cutti ng could be done in bot h direc­ tio ns of the tab le travel at equal speeds . or in one directio n with a qui ck return the o ther wa y. Each of the four too lheads had pow er operat io n independent of tab le mo ve ment, so that cross-p lanin g cou ld be done through bearing recesses . etc. One of the pictures show s this operation on a model be ing do ne by m ill ing. Each

head co uld also be swive lled so t hat ang ula r faces could be planed also . After the planing of crosshead slides they we re tackled by the fillers and scraped to a portable surf ace plate. Thi s was coa ted sparing ly with a mixture of lam p black and oil. slid to and fro on the slide . li ft ed off. and then all the black marks scraped away. The surfa ce plate w as then put on aga in and a fresh lot of marks mad e. w hich in turn w ere scraped away. This work went on for many hours, indeed on a big slide tw o m en cou ld spend two or th ree days. For such work the surface plate wo uld be so large th at two men cou ld not lift it wit hou t the use of the shop crane. Even tuall y afte r a lon g t ime t he fi nish obta ined wou ld b e rega rded as acce ptab le. It then consisted o f a very large num ber of extre me ly shal low depressions bet w een the marks . and each of these proved to be an oi l

Fig . 22 Milling bearing j aw s in bedp la te

32 33

pocket. When the engine was eventually pu t to work, with the cross-head hav ing had similar treatment. the resu lt was that the cross - head ran to and fro on a film of lubr ican t which reduced wea r to a very small amou nt. Engines in textile m ills would run 60 years and at the end you would find the scraper marks still there . T he oil was continuously renewed by brass combs attached to the crosshead which picked up oil from a well at each end of the slide . An eng ine running night and day. as many of them did . with a

speed of about 80 r.p.m. would make approx. 3600 million cross-head strokes in that time! No t a bad performance? When flat surfaces have to be produced at rig ht ang les to the table it is necessary to use the side of an endm ill . Th is may be quite unavoidable on some components, suc h as the model eng ine bedplate shown in Fig. 22 . There is not much choice about milling out the jaws for the crankshaft bearings. This is an operation wh ich the big planer used to do with the power drive on the heads of the cross -rail.

CH A PT ER 3

Slitting and Cutting It is common practice to des ign mac hinery components with spli t bosses w hich can be contracted with a screw for tightening purposes. The slitting can be do ne with a hacksaw. bu t if done in unskilful fashion will not look good when completed . Slitting saws and many other disc type cu tters can be readi ly used on the vertical mille r by mounting t hem on a Mo rse taper arbor having a pa rallel portio n for the

cutter, and a nut to secure it . Its a good thing to put a pair of flats on the arbo r to hold it by when turning the nut. Fig. 23 shows a slitting saw in use cutti ng through one side of the boss of one of the parts of the Quorn grinder. On t hat machine there are several components w ith this feature, so time will be saved if they are all col lected and cut th rough while the saw and vice are in position.

Fig. 23 Slitting boss of casting

34

35

M any o th er jo bs of simila r nature w il l co me to m ind, suc h as engi ne eccent ri c sheaves, and especia ll y ecc ent ric straps . wh ich can be cast in one pi ece and the n cut thr oug h, leavi ng two surfaces that need only a to uch with a fi le to rem ov e

burrs to enable th em at on ce to be bolted together. Not on ly are castings inv olved but also parts ma de from bar material. Ma rin e type connecting rod ends are an example. and this method can also be used for producing bearings in halves.

CHAPT ER 4

Keyway Cutting

Keys and keyways are a v ery co m mo n feature of machi nery and naturally of mod els too. Th e comm on ro und-e nded keyw ay. for a 'feather' key . is easily produced on a parallel sha ft by hol di ng the shaft in the vice and using a sma ll end mill , or two -f lute 'slot -drill'. Fig . 24 show s the set up for this ope ratio n. Various parts of car and motor cycl e

engi nes. gearboxes, and other machi nery compone nts in the past have had whee ls mount ed on tapered shafts wi th the keyw ays foll owin g th e slope o f th e taper. M odellin g one of these w ou ld involve fo llo wi ng the same proce du re. One way in wh ich this can be done is shown in Fig. 2 5. The vice holdi ng the sha ft is set on a tilting angleplate so th at the top o f the

Fig. 24 M illing Ieet her keywa y

36

37

Fig. 25 Millin g fe at her ke yway on tap er ed sha l t

tapered pa rt com es pa ralle l w it h the m achin e t ab le. The shaft show n in t he pictu re is a sim ple on e and q uit e short . and could have been j ust t ilted in t he vice in a set-up like t hat of Fig. 24 . But a long shaft m ig ht well fo ul th e t able at it s low er end so t he elevation which t he ang lepl at e gi ve s co uld in such a c ase prove essent ial. Sma ll endm ill s are rather frail to o ls at best and li able to easy breakage . The di sc ty pe cutt er is more rob ust and a co ll ecti on of these acquired either as the need fo r one crops up , o r bo ug ht cheaply seco nd ­ hand, is w o rt h while . Of co urse th e d isc cu tte r canno t always go clos e to a shou lder o n t he shaft , and copying a pro totype may in some cases rule it o ut . For th e w o rk do ne in t he hom e workshop t he re is no need to insist on the rel ativel y expe nsive side - and -face cutt ers, (t hose with te et h on t he f aces as w ell as th e pe ri­ phery ) because the sli tting saw , w ith te eth o nly on t he periphery, w il l do qu ite wel l. T hese are m ad e in a very g reat va riety of

38

t hicknesses , an d are always co mi ng on t he surp lus m arket at low prices. One of t hese is shown in Fig. 2 6 m illi ng an ord inary sunk en keyw ay, th e shaf t bei ng held in a vice wi th eno ugh ove rha ng t o avoid t he cutt er t ou chi ng t he vice.

Fig. 2 6 M illing keyway w ith sli tt ing saw

For a sta rt the key itself can be part ed off fro m a piece of ro und mi ld st eel or silver st eel. So it s d iam eter is sett led w it h

ac c u racy f ro m t he b ri ght ba r. T he thi ckness need s careful co nt ro l, but if it com es off a b it t oo t hick it can be rubbed

Fig. 27 Set 01 four W oodruff ke yw ay cutters

WOODRUFF KEYS The Woo d ruff key is on e w ide ly used in ind ust ry . This is in effec t a slic e off a roun d ba r, cut in ha lf and set in to t he shaft in a recess m ad e by a sma ll d ia m eter slitti ng saw . Th is is rath er an oversim plified des cr iptio n , but it wi ll serve we ll enoug h as an int rod uct io n to the W ood ru ff key fo r thos e in ho me w o rks h op s w i t hou t ind ust ria l ex perien c e. Se riou sly . th e W ood ruff key. w hic h I t hink was of A m erican or ig in, has som e ve ry real ad v an t ag es for th e m ass pr o d u cti on ind ust ry , and so me of t hes e are of just as gr eat im po rt ance in t he home wo rkshop and t he fi eld of lig ht en gineerin g.

39

down on a flat file . It needs t o be cu t in tw o on a lin e w hich is nearly a dia me te r, but the cut edge can readily be filed to br ing it to fina l shape . Th e keyw ay is made by a simple cutter like a slitting saw, of the same diameter as the ba r from wh ich the

key is ma de, with an int egral shank of pre­ ferably some sta nda rd di ame t er w hich can be run true in a collet on the mi ller. So the shap e of the keyw ay pro fi le - and its w idt h - is settled by t he cu tter form . The cutti ng par t of the cutter is set in line w ith

TABLE II

G~

2

the diame tra l li ne of the shaft. the n th e cutt er is fed in by a predetermined amount. The resulti ng keyw ay is deep enoug h to give the key a good ho ld , so that it cannot roll over, and yet the shaft is no t unduly wea kened. Norm all y th e t op o f the key is just clear of the keyway in the wheel or lever wh ich is being secu red , it s purpose bei ng to provi de eit her tor qu e or angular locat io n, and some mea ns such as a grub screw may have to be used to preve nt endwise movement. W ood ruff cutters are not very ch eap , but they can easily be made in the home workshop, from silver steel. The process is really qu ite sim ple. A blank can be turned , mak ing a shank to sui t some sta nda rd collet. then with the sha nk held in the colle t th e working part of the cutte r can be turned to it s diam eter, and th ickness. The sides sho uld be very sligh tly undercut by setting a kni fetool a little off square. Using a sim ple un-gea red dividi ng head th e

teet h can be cu t in two ope rations using an ordinary end mi ll ; the re is no need for angu lar cu tters. as t he d iagra m on the opposit e page indicates. The num ber of teeth is no t importa nt, but six is a co n­ ven ient numb er for small cutters . It is possible to file the teeth if you do not have access to a div iding head. as the spacing is not at all critical , but it's a little more difficult. Fig. 27 shows a batch of cutters made to the sizes in Table II and Fig. 28 shows a keyway being cu t . There seems to be no place where sizes of Woodruff keys and cutte rs are disp layed for m odel engi neers . Machinery 's H andbook giv es sizes wh ich are used in ind ustry. but the shee r range of sizes is itself confusing, and of cou rse t he tables are libe rally sprin kled wit h to lerances that model lers cou ld neither follow no r wa nt . I have therefore picked ou t a few sizes wh ich I think wi ll serve ou r pu rpo se. and as we don 't have to provide interchange ability in our products, if anybod y w ant s t o depa rt a bit

Fig. 28 Milling Woodruff keyw ay

3~ x20 B.S.F. FOR F CLARKSON Be. OSBORN CHUCKS.

WOODRUFF KEY S & KE.YWAYS

A

B

~ 44­

I

~6 3-'8 ~

2

40

C

D

CUTTERS

E

F

'10 9 '073 '037 '10 0 .% .6 140 '/ 0 4 '03 7 '/04 %2­ '172 '/23 '053 -/ 29 ~ 2 -203 '155 '053 -1 87 -(6

G '030

'037 '04 5 '0 60 41

from t hese di mensions he can certai nly do so. Up to date of w ritin g I have not seen any spec ifica tion of W oodruff keys in met ric sizes. The cutters shown in Table II hav e screwed sha nks to suit Clarkso n and Osbo rn chucks, wh ich have colle ts th at close on the cutter shan k throug h end th rust exerted by the cutter agai nst the inside of the chuck. If you are maki ng cutters for use in a Clare chuck or just to use in a 3 -j aw . these thr eads are not needed. It may be noticed that the cu tters

sho wn in Fig. 27 are stamped w ith thei r size de tai ls. It is a goo d plan to have a set of small stam ps. say 1/1 6 in . character s. so that appropriate identity can be mar ked on all hom e m ade tools. jigs. etc as we ll as model co m po nents. The hol es dr il led in these cu tte rs were provided fo r the co n­ venien ce of the har dener . They were harde ned for me by a firm where liq uid ­ salt bath s are used fo r heat ing and q uenching tools. A sma ll hole enables the tool to be hung on a w ire in the bat hs w ith out da mage to cutting edg es.

CH APTER 5

Fluting Components other than Tools Fluti ng of locomotive con necti ng rods and coupli ng rods is an operation very sim ilar t o keyway cu tting so fa r as th e rem ova l of me ta l is concerned. bu t the leng th of the flutes is usually greater, and th e lengt h of the pieces de man ds som e w ell arrange ho lding m ethods. One occasiona ll y sees rods which hav e been fluted w ith an endmi ll by the same metho d as show n in Fig. 24. giving rou nd ed end flute s like a feath er keyw ay. Thi s is ent irely wrong . no full size rods w ere fluted thi s w ay. They have flutes w ith rounded int ernal corne rs in the bot tom . and wi th swept out t er­ m ina tio ns at the ends, whi ch is done to avo id the notch fatigue cracks w hic h can propaga te fr om sharp co rners. Fortunately it is qui te easy to produ ce flutes whic h are in acc ordan ce with full size practice. and not even necessary to have a fancy m ill ing cutl er. A simp le tool bit, gro und rather lik e a partin g too l. wi th the corners rou nded off. is put into a transverse ho le in a cu tler bar , and m ounted in a chuck on th e mil ler. Th e rod to be dealt with is fixed edgewa ys up , as it go es in the loco . prefe rably aga inst a long ang leplate . and th e rotat ing cutle r is fed in like a W ood ruff cutler wou ld be. Wh en in to proper depth. usually quite shallow, the ta ble move ment is started and th e flute is then made

p rogress ive ly alo ng th e rod , leav ing behind the swe pt end . Wh ere the cut fini sh es there is als o a swep t en d, autom atica ll y. Coup li ng rods usua lly have flutes that are parallel sid ed, and so do some t ypes of Canadian and Am eric an con nec ting rod s. In these case s a single pass with a cutle r th e right w idt h w ill c om p lete t h e jo b. Mo st Br i t i s h locom otives . on th e ot her hand , had tape red con nec ting rods wi th parallel flanges . l.e. tapered flutes. For these tw o passes are need ed. and th is can be achieved in a very simpl e w ay. In Fig . 2 9 the rod of a Canadi an engi ne is seen fixed on th e ang leplate. In eac h end is a screw with a head tu rne d to th e size of the ho le in the rod end. Thi s is a 12 in. lon g angl eplate wi th no slots. as hol es are drilled and ta ppe d just w herever they are needed for each job. It w ill be many years before it is so perforated as to be no fur ther use. The two ho les for the locating screws are th e same dista nce from the table. and they only provide the locati on . the rod being secured agains t t he cu tting forc es by two sma ll clamps as shown. For this rod and for coupling rod s the set -up is exac tly as shown. But for British type rods . the screw in the big end is made smaller than the hole in th e rod by the

42 43

CH APT ER 6

Boring

Fig. 29 Fluting locomotive conn ec ting rod amou nt of the taper (at th e hol e centres) and for the first operation th e rod can be allowed to dro p down o n the screw whi le the fi rst cut is t aken. Th en for th e second cut the rod is lift ed up as far as th e screw w ill let it go . and re-c tarnp ed. and a seco nd cut taken, The rod w ill now finish w ith a taper flu te and two parallel flanges. Th is fluti ng is a very simple ope ration . The angleplate is extreme ly rigid. The mach ine in the pi cture is happily provided wi th a in. w ide keyw ay alo ng the centre of the table. only t in. deep . but a i- in.

t

square ba r can be dr opp ed int o it. That enables fixtures to be instantly lin ed up w it h th e t ab le movemen t . in c lud ing dividing heads as we ll as ang lep lates. The thrust of the cutte r in this example tends to move the ang lepl ate awa y from the bar . but it is secured w ith tw o good bo lts in t h e t ab l e slot s . n o t v isi b le i n t h e pho tograph. It sho uld not be forgo tt en that locomotive rods w hich are flu ted at all m ust be done on bo th sides. but wi th a set- up li ke this the job is so simp le it w ou ld be a pity not to have it righ t.

It is not uncommon t o have bor e holes in com ponents w hic h are m uch too large to sw ing around in the lath es that are fo und in mo st ho me workshops. But there is no need in many cases t o resort to hand too ls. even for ho les w here great accuracy is not needed. Th e vertical mil ler can be used for boring (w it h a trepanning tool in a bo ring head) such th ings as fire- hole do or s in bo iler plates. bosses o n castings suc h as lon g levers. and many o ther ob jec ts. In or der t o rnot ori se a shaper I had to bore a hole throu gh t in . o f cast iron t o mo unt a worm reduction gearbox . and t his had to be a true round hol e. It was do ne by fix ing t he cast ing (15 in. long in one direc tion fro m the centre o f the

ho le) on the mil ler tabl e and using a cutt er in a boring head. W ith the w orm- actuat ed dow n feed. and the bot tom spe ed of th e Dare-Westbury m achine. 3 4 t rp m . an excellen t hole wa s obtained four inch es diame ter. W ithout th ese facilities t he work wou ld have been sent out to som e engineering firm . Th e am pler space on t he tables of m il ling machines. com pared w ith w hat one can get on a lathe saddl e w ith an angle plate . makes the miller invaluable for w ork of thi s ki nd and of cour se by do ing externa l tu rnin g w ith a boring head one can dea l w ith male regist ers as we ll as hol es. This is a simp le op eration too ; on e just turns the cutt ing tool inw ard instead of outw ard.

44 45

CHAPTER 7 .

t\

46

6+

=::--­...,."

J ig-Boring The ter m 'j ig-boring' is lik ely t o be unfa m iliar to m any readers of this boo k, and they may thi nk that w hateve r it mean s it m ust be a lon g way removed from model engineering. This is no t so, for in model m aking pl enty of operations arise th at can be don e by 'jig-boring ' to adva n­ t age. Basicall y it only means fixi ng a com ­ ponen t to t he m ach ine tab le and th en using the tab le screw s as measuring dev ices to positio n the spindl e over any part of th e com ponen t that is desired before dr illi ng or boring a ho le. In m any ways t his m eth od is better than m arking out, measu ring wi t h a rule, then centre­ pu nch ing fo llowed by drill ing on a drilli ng machine. For one thing th e wo rkp iece is fi r m ly held , t he t ab l e screws are reasonably goo d measuri ng devices, and man y ho les can be m ade, of any diameter needed. without losing the att itude of the piece to the table, or on e hole to another. Let's take a fairly com mon componen t, the beam cast ing of a mode l bea m eng ine . This will have severa l holes to be dri lled , usual ly along one straight line. and rather impo rtan t. all these shou ld be parallel wi th one another if the finished engi ne is to run smoothly. There will be one ho le at each end , and a main trunnion ho le at the middle, plus one or more for the links of

a

~--"

the pa rall el motion, pump rods, etc. The casti ng can be cl am ped t o the ta bl e qu ite firm ly, resting on pack aging of reason able thic kness so that a penetrati ng drill do es not dip in to the t able. A t th is stage all bosses can be faced w ith an end m ill , even if they are at differen t levels. Th e centre lin e of the cast ing should have bee n set paralle l w ith the line of the t able movem ent . Put the drill chuck in the spind le. w ith a fine point ed du m my dri ll sim ilar to a ce ntre punc h. and br ing this over the first boss cen tre . The n wind on th e table the amou nt t o t he next hole and check if the point com es in the righ t place ove r that boss. W ind on again to th e next and so on check ing at each boss. If all com e cen tra l. all is wel l. If one or mo re don't. then an allo w ance w ill have to be m ade as a co m prom ise. Ma ke a not e o f wha t it is. re-start at the begin ning, and do another run till you are satisfied you have got t he rig ht starti ng point for the best results. If yo u happen to tu rn the ta ble screw a bi t t oo far at one of the stopping points, do n't worry, but do n' t turn it back a bit as a correc tion , because th at way you cou ld introd uce an error thro ug h back lash (lost mo tion due to slackness) in the screw and nut. Go back to the very start and com e at it again. It's a good thing

,..,38

I~ ~ ~:

-+--II-- -005

I

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Fig. 3 0 Drawing of stea m hoo k (l ever)

w hen do ing an exercise o f this kind to have a paper and pen cil handy and w rit e dow n the m icrom et er dial readings w hich are th e st opp ing points. This redu ces the ch ances of acciden t al erro r. It is a method used by men in industry w ho are engaged on delica t e w ork w here a mom entary in t erru pti on ca n be disast rou s. I have my self used it for m any year s. A t th is stag e drillin g can no w sta rt . Each hol e should be centred w it h a D-bi l groun d to about 1 18 degrees, foll ow ed by the app ro priat e dri ll. thoug h th e larger holes may need a pilot dr ill put ting through first . As eac h hole is fi ni shed. w ith reami ng if needed, move on to the next hole by the table wi nd. and go th ro ugh the procedu re with th at. too. By this meth od all the holes w il l be the rig ht distance apar t , and w ill all be pa ralle l to one another in tw o plane s. It w ill be clear th at if any holes are wanted which are no t on the m ain centre line, it is a simp le m at t er t o drill these in an off-set

positio n by using the table cross-screw to provid e the amount off th e m ain line. W hen all the ho les are fin ished t he beam can be tu rned over and the bosses m ill ed on the other side . Th e beam eng ine casting is ju st one example of ho w t his sort of t ask can be handled. Fig. 30 is a draw ing of a co mpo­ nent of th e t rip gea r of a model steam engin e. and the holes w hic h have to be drilled are in posi tion s w hich w ou ld not be easily att ained by the co m mon marking­ out and centr e punching proces s. Fig. 31 shows one of th e finishe d pieces w it h one only part-ma de , to show th e me thod adopted. One inch diame t er bar wa s used . as that gives th e outside profile needed. Set true in th e fo ur- jaw chu ck it was bore d 9/ 16 in., the n set out of true by .047 in . and the ho le re-bored to the same setting . Next it was set well off centre to dril l the No. 38 drill hole. Th e correc t setting was established by measurements 47

taken off the outside surface of the 1 in. bri ght ba r. With the pi ece still held. the chuck w as removed from t he lath e and bolt ed on the m illing mach ine tabl e. A number 3 8 dr ill . ru nning i n a tru e chuc k. t hen 'picked up' th e existing hol e and the di al readin gs on both screws of the ta ble w ere no ted {and w ri tten do wn !' The drill was chan ged for a very sho rt stiff 1/ 16 in. drill. the t able screw s were ro t ated . to bri ng the first 1/16 in . hol e pos it io n un der it and tha t hole then dr illed. Further rota tio n of th e scre ws brought in turn each of the o ther holes into pos ition and the drilling wa s quickly com pleted. The chuck was then re turned to the lathe. Th e fi rst boss around the No. 3 8 hole was turned and t he piec e parted off. care bei ng taken to leave the shallow boss on the part ing side. Then the second bos s w as turned . anot her parting off . and the two com po nent s w ere th rough t hat part of the process. It rem ained only to cut the desired piece out of the ring and file up the two ends t o t he rounded profile. By these met hods a com po nent of a rather com pli cated shape w as produced und er

co mplet e co ntrol and exactly as specifi ed on the drawi ng. There are m any o ther artic les in model engi neering wh ich lend them selves very w ell to th e jig-boring techn ique. Locom o­ tive boiler tube plates w ith a large num ber of holes can be do ne this w ay. and becau se som e of the hol es m ay be in. or even mo re in di am eter it is vita l to have th e m et al c lam ped do w n t o avoi d pe rsonal injury . as copper is not one of the kindes t of m at erials for machi ni ng. But if cl ampe d on packi ngs o n the m iller. any large holes for w hich dr ills are not avail­ able can still be dealt w ith by using a boring head. If a large drill is available. and th e m achine has a low enough spee d t o avoid chatte r. there w ill be no 'three­ cornered' holes ma de to cause em barrass­ m ent w hen fittin g flue tubes and silver­ soldering th em at a later st age. It w ill be fo und that as fam iliarity w it h th e vertical mi ller dev elop s. other exam pl es wi ll aris e in w hich this high- soun di ng but really qui te simple technique can be bo rrowed fr o m ind ust rial p ract ice. w i t h g re a t benefit s.

t

Fig. 3 1 Photograp h of st eam hook

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48

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CHA PT ER 8

Profiling

It is not unusual for large compo nent s to have po rti ons w hich are ci rcular arcs , Loco m o t i ve f r a m e s a r e co m mo n exam ples. w it h cut -aw ays t o cl ear bogie whe els. Such pi eces are m uch too large to sw ing in th e lat he. and wh ile the bandsaw if available can do a lot t o relieve the tedium of drilli ng. hack saw ing and filing. the miller can do a lot mor e. Using a trep anni ng cutt er in a boring head it can take aw ay the unwa nt ed metal in a single operation to finished size on any arc. A lte rnatively w it h a bor ing typ e tool it can follow th e bandsaw and just avoid th e filing. Smokebo x castings for locom otives and tractio n eng ines. how eve r, oft en have circ ular arcs t o fit the boiler she ll. and the bandsaw can be nohelp wit h these. But if they are set up on th e mi ller. th e radi us can be de ter mine d by the sett ing of a bo rin g head cutt er. and trave rse across the wo rk provided by th e downfeed of the spi ndl e. eve n t houg h th is is us u all y m anual. Th at feed lengt h m ay no t be eno ug h to cover t he face wid t h, but aft er going as far as th e spindle w il l move. a second cu t can be taken by resetting th e head of th e mach ine . I n m ac h i n e r y de t a i l s t h e s a me probl ems arise. Fig. 32 shows a pad bo lt

for locki ng tw o ma chine parts togethe r. Th e two part s of th e pad bolt w hich are being pro fil ed t o suit a rou nd col umn we re made fro m one pi ece of steel. and cut apart afte r th e profilin g. A gro ove can be seen w her e t he separating cut wa s to be taken. The cutt er in the bor ing bar w as set to t he fini shed radius. Only the cross-feed of the t able was used (to put the cut on bi t by bit) th e other slide being loc ked. The tool w as t raversed by the down feed. It is no t pos sible to tak e the full am ount of metal remov al in a singl e pass in a job like t his, but w ith succe ssive cuts a perf ec t job is assured. Sim ilarly the hol es for such pad bol t s are 'part ho les' and could not be dril led in the second st age to full size w ith ou t gui de bus hes for the dril l. But drill ing under size and th en open ing out with a bo ring head get s there just t he same , a bit less qu ickly. Prof iling loco moti ve connec ting rods and coup ling rods can be a somew hat t iring operation if one has t o do it by sawi ng and filing. Trying to do this w or k on the bo ring table of th e lathe wi th vertica l slide or angleplate is not very happy eith er. Usually the cross- slide travel is mu ch too short to co mp lete the length i n one p ass. so t h a t re - se tt i n g is necessary . and th e lath e doe s not have

49

th e in-feed faci lities needed. Gene rally with a vertical slide the poi nt at w hich cutt ing is be ing done at the end s of a long rod is a very long w ay fro m th e place where the sli de is secured, so that apart from 'spring ' of th e pi ece there is dange r of slipp ing t aking pla ce with dis astr ous result s. Com pare such attempts w ith the

set- up sho w n in Fig . 33. w her e a pair of co up ling rods . w ith 'chucking pieces' o f extra me ta l at each end , are clamp ed on packings in a safe and rigid set-up . Generally th e di am et er of end m ill used can be arrange d to give the right radi us where the body of t he rod jo in s the boss es.

Fig. 32 Profiling pad bolt

Fig. 33 Profiling coupling rods

50

51

CHAPTER 9

End- Rounding In model work, as in ful l sized machinery , many comp on ents such as crank webs, connecting and cou pling rods , m achi ne links, etc. have to have rounde d end s. These can be produced by fili ng, and th e use of hardenerd steel collars and roller s for gu ides has oft en been reco m m ended in Model Engineer t o help th e not-sa-good file r to achieve a good appe arance. Even wi th th ese, this kind of filing dema nds a skill wh ich many modellers jus t do not have (and wi ll never acqu ire, for wa nt of practice, if nothing else) so for th at reason alon e it is not a good m et hod. But it is also rathe r seve re o n fi les, w hich are now qui t e expe nsive too ls, and unlikely ever t o get che ape r. So w here t here is a vert ica l miller avail­ able, w hy not do the job th e rig ht w ay. as it wou ld be done in com me rcia l eng ineer­ ing ? It me ans investing in a ro tary tabl e. but th ese can be bo ug ht in kit form as we ll as co mp le t e read y for us e. and if mach ined and assembled by the hom e worker himself. are not terribly expensive. Presum ing th at the com ponent has a round ho le at one end . a plug is needed in the ta ble so as to loc at e by th at hol e. I have a sm all ro tary table w ith a t W hit. ho le in the cent re and have a number of plug s of sta ndard sizes to fi t tha t. Bu t 52

ano t her t able wh ich I have poss esses a No. 2 M orse tape r centra l hole and arbor s can be put in this for loca tion. It is. in fact , a Model Engineering Services Type RT3 wh ich does not have a t ee-slo tt ed table, but has a spindle screwed lik e the M yf ord lathes and will accept any chucks or faceplates from the lathes. This ma kes it feasible to turn , say, a cy linder cover and transfe r it to a rotary tab le fo r dri lling the bo lt hol es wi thou t losing the accur acy of setti ng , Bu t th at is not a featu re of impor­ tance for round ending operat io ns. I have used it for a numb er of engi ne cranks in th e manner show n in Fig. 34 . Each crank was located on the arbor but also cla m ped w ith a slot plate resti ng on Picado r step ped packings, a pa ir of these be ing also unde r the crank itself. The cutte r is a t in. end m ill cutt ing on it s side . In all ro tary m illi ng of this kin d w here the cutter is work ing on the outs ide o f th e com ponent it is vit ally necessa ry to feed the ta ble cl ockwis e seen from abov e. All no rma l m illing cu tt ers rot at e the same w ay as a twist dfl ll, so wh ich ever side of the work the cutte r is touching, the w ork mu st meet the cut te r. and t hat means clockwise ro tation is essenti al. Oth erwi se if the cutt er is goi ng the same w ay at the surface as the work it is certa in to grab

Fig. 3 4 End-roun dinq with rotary table hold and tha t mean s at least spo iled work. probab ly a brok en cu tt er. and a lot of g rief. But if one is w orki ng on an int ern al pro file, such as trimmin g the ins ide of th e rim of a flywh eel. th en th e forces are reversed and th e w ork needs rotat ing ant i-clockwise. No w the threads of th e RT3 spi nd le are like th e M yf ord lathes. righ t hand , so wh en one is do ing insid e work a chu ck or facepl ate is tight ened by the thrust o f th e cutter. But w hen do ing the. perh ap s, more no rm al m ill ing on the ou ts ide of a piece, the cutt er th rust tends to un do th e faceplate. and unless the work is very light cutti ng. this is w hat w ill cert ainly happen. T he only satisfactory answer to thi s problem is to drill and tap a hol e thro ug h th e bo ss of the faceplat e. m ake a coned di mp le in th e t able spindle at the sam e spot, and insert a screw with a co ne po int that fit s the dimple. No t a diffi cult mat ter at all. But if you are going to use a chu ck on the sam e table for th e sam e kind o f work, the n m ake a penci l m ark to show wh ere the dim ple is for the faceplat e, and

drill the chuck boss w ell aw ay fr om th is, so th at you have tw o positive ly sepa rated dimp les, each for its own accessory . I have used a 5/ 16 in. BSF sock et grub screw for this purpo se. with a po int modified (in t he lathe) to a lon ger co ne. Bu t I fo und th e or dinary hexagon key w as no t really long enough to be conveni ent with a standard 7 in s. Myford faceplate. So I cut off th e shor t bent end of th e key and fitt ed t he long part to an exte nsio n made of 1 in. brigh t mi ld steel. This was drilled in the lathe 3/ 16 in. deep w it h a No . 16 d rill wh ich is about the acro ss­ corne rs size of th e hexagon , then 7/ 16 in . further w it h a No. 22 drill wh ic h is about the across-f lats size. The tw o pieces w ere th en pressed togethe r in a big vice , the squared-o ff end of the hexagon cutt ing its way down t he hole in t he m ild steel. A 5/32 in. cross pin w as fitted. Loctit ed in, and now I have a Tee w renc h long enou gh to reach the screw in the boss without any difficulty. It took on ly fiv e minutes to m ake and is a convenience there for ever. 53

CHAPTER 10

Dividing Heads

For m any products the use of a divid ing head is an absolut e necessity. M any ho me workers, especia lly those w it hout any engineering experience, rega rd th em as mos t myst eriou s devic es. almost border­ ing on the occ ult, and say wi thout reall y thinki ng, 'Oh. I cou ld never use one of those !'. We ll , a dividing head is really no more than a headstock w ith a spind le on w hich the wo rk is mou nt ed, w ith some m eans o f turn ing it through po sitive angula r amou nts , and holding it there wh en each movement has been made. Nat urally th ere are m any types of div idi ng head and over the years many de signs have appeared in M od el Engineer for heads w hich can be m ade in the home w o rksho p. A g r e a t dea l o f qu i t e sat isfactory work can be done w it h a sim ple head of th e typ e shown in Fig. 3 5. On the spi nd le, provision is made for mou nting a lathe cha nge w heel. A spring­ loaded plun ger wit h a conic al poi nt drops into th e gap between tw o teeth of t he w heel, and then the spindle is locked by a screw bearin g on a pad inside the ma in bearing. I t is advisable not to rely on t he plu nger hol d i ng the spi ndl e agai nst rot ation when scre w ing on chucks of w hen fixi ng a co mponen t on an arbor by me ans of a nut. If the spind le turns, t he

teet h of t he change w heel m ay be badly dama ged. In fac t w hen do ing th is sort o f fixing I alw ays diseng age th e plunger, the n if the screw pad doe s no t hol d. no damage is done . By selec ti ng a suit able ch ange w hee l it is pos sib le to get quit e a lot o f divisions very easily. For example a 60 toot h w heel w ill gi ve 2 . 3 , 4 . 5. 6. 10 . 12 . 15 . 20 or 3 0 divisions. It w ill no t give 8 . but a 40 tooth w heel w ill do so. W hen doing dividing w ith thi s kind of device it is a go od thin g t o have a bit of chalk handy and mark the appropriat e toot h gaps w here t he plunge r is go ing to have to drop in, before starting cu tti ng, to avoi d i nco rrect settings w hic h wou ld spoi l the w or k. Ma ny examp les of m achinery parts to w hic h a sim ple head of this kind can be usefull y applied cou ld be given . Suc h it em s as cr ankc ase dr ain or filler plugs wh ich need hexagons. square ends on shafts, tools like ta ps, reamers. pa ralle l fl at s f o r sp anne rs on ro und art icles, all th ese can be fo rmed so very easily with an end mil l, w ith less phy sical effort than fil in g, and w it h an accu racy w hic h enha nces th e appearance o f th e arti cl e even if dim ension al accuracy as suc h is no t im port ant. But there are examp les w here accuracy is fairly im po rta nt, and on e w hich cou ld

hardly be don e at all w it h hand tools is shown in Fig. 3 5. This is one half mem ber of a dog clutch . The 12 teet h are bei ng cut with a slitting saw w hich passes across the work right on the centre line. Aft er each cut . the locking screw was eased . the plung er lifted out, th e w heel turned five teeth . and t he plunger dropped in aga in. The spindle was then locked and the next too th gap cu t. Really a very simple procedure. Now on the o the r ha lf member of t he clutc h the teeth have to have pa rallel sides, and the gaps them­ selves are t aper sided. This just involves sett ing the cu tt er with its bott om edge above the cent re lin e by half the thi ckn ess of t he teet h left upstanding in th e first half. T he same procedu re of cutti ng right acr oss is fo llow ed . and afte r six passes th e job is co m plete. It is feasible. if yo u are wi lling to t ake the trouble. to make a clutch w ith all tooth side s t apered. so that the two halves are ident ical. If maxim um

stre ng th w as needed to transmi t a lot of pow er this mig ht have to be done. but it is a good dea l mo re difficu lt and would rarely be w orth the trouble. Unless yo u are using a we ll-es tablished desi gn for wh ich draw ings are available. it is advisable to layout the tooth design on the draw ing boa rd , prefera bly at an en larged scale. to verify the thickness o f cutte rs w hic h w ill produce th e desired result. They may be the same thickness fo r bo th halves. bu t maybe not . it depe nd s on the thickness of too th selected. It is also a goo d thing to avoid an odd num be r of tee th. bec ause the curve of th e cutt er w hen going through one side may be chew ing int o the met al whi ch has to be left int act on the opposite side to mak e the too t h. If your des ign can arrange for an eve n number of teeth this risk w ill be eli m inate d. A not her poi nt is to chec k t hat th e desired number of t eeth can reall y be s ecured wi t h the dividing head you int end to use.

Fig. 3 5 Cutt ing teet h in dog clutch part

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M YFO RD DIVIDING HEAD The Myford dividing head is an exce l­ lent piece of equ ipment, w ith a very w ide range of divisions. The main spi ndle has a 60 tooth worm wheel on it. and a single­ start worm meshes with that. Concent ric with the worm there is provis ion for mounting a m ult i- holed division plate which remains stationary and does not rotate w it h the wo rm . On the worm spindle is fitted an arm carrying a spring­ loaded pl unger wh ich has a po int of paral lel shape that ente rs holes in the divi sion plat e . This arm is slotted and can be set to such a radius as w ill br ing the plunge r in th e right place for any of the row s of ho le s that are already drilled in the plate . H aving set the arm. if one tu rns the w orm one w hole turn and drops the plunger bac k int o the same hole fro m w hich it star ted , the m ain spi ndle w ill have rot at ed one sixt ieth o f a turn. But if on e m ov es t he w o rm and arm fiv e comp let e tu rns befo re droppin g in, the ma in spindle will have turned one tw elft h of a tu rn. Basically. that is all there is to getting any desired number of divisions. Hav ing got the right division plate on the head one moves the arm so m any turns, plus if necessary, a certa in num ber of holes extra to the comp lete turns. A chart supplied wit h the head giv es all the avail ­ able co mbinat ions. In order to accomplish all divisions up to 100 it is necessary to have 4 plates . but two of th ese are needed on ly for some rather out landish numbers with whi ch few mode l engineers w ill ever have to deal , so the two normal plates w ill serve. almost every thing. There is on e point of practi cal imp ortance in using a

STE A DY STAND fO R MYFOR 0 Dlv'O'G HEAD Opposite, Fig. 36 Drawing of st eady stan d for M yford dividing head

56

w orm gea red dividi ng head . Whe n moving from one positio n to the next. always turn the worm the same wa y, never go bac k. If by chance you overshoot t he rig ht hole . of course you have to t urn back. but go we ll bac k. way beyo nd the hole you want by a good margin . the n come up to it afr esh. If you fail to do this you wi ll have an erro r in your dividi ng and a scrapped work -piece. Our old enem y 'back- lash' wi ll see to that. But it' s easy enoug h to avoid th is kind of disaste r. Th ere is provided on the head a most im po rtant aid to co rrect co unti ng of the number of holes needed w hen turning the worm . Tw o brass blades are fitted around the worm shaft . above the divis ion plate, and these can be moved relat ive to one anot her, by loosening a screw, and set to em brace th e num ber of holes needed. Th an afte r lockin g w it h the screwdrive r, they make a mask to sho w just where the plu nger sho uld be dropped in . A fter each movem en t you rotate them ti ll one blade comes aga inst the plunge r, and yo u are the n ready (afte r doi ng the cutting of cou rse) fo r the next move. In this pa rt of the procedure the two blades move together as if t hey were one piece of met al.

STEADY STAND I have found in using the Myford head that it is a convenience to be able to set it at lath e centre heigh t when fixed on the boring table. If one wants to drill cylinde r covers and simila r work the radius of th e row of holes can be readily obtain ed by the cross slide screw and th e measure­ men t is direct. So I have a packing block of the right thi ckness whi ch I can place under it for th is purpose. There is one minor cr it icism of th e Myford head which is never theless impor­ tant from a pra ctical po int of view. Th e single bolt wh ich holds it to a machin e

57

tab le or vert ica l slide , etc . does on occa sion come a lo ng way from the poi nt whe re cu tt ing is being done . and accor­ di ng ly there is da nger of the work being spo ilt by the head slippi ng. To ove rco me this I have made up a st eady stand from mi ld stee l bar m ateria l wh ic h bol ts on t h tab le o f the m ill er, and clamps on the 1 in . overarm ba r of the head. The st and has a vertic al t in. ba r set into a fl at base with slot for a table bo lt. A tw o-w ay cla mp slides o n thi s vertical bar, and ano ther t in. b ar passes through it horizont ally. A t the end of this is a two- plate clam p ripping the t in. ba r, w it h provision also

for gripp ing the 1 in. bar o f the head. The various clamp s can be mo ved separately and make a pretty unive rsal fi tt ing. The wh ole thi ng is shown in use in Fig. 3 7 . Th is fitting of my de sign is no t on the ma rket , but it has proved so useful to me that I am giv ing a working drawi ng of it in Fig. 36 and anybody who likes can make a unit fo r hi msel f.

OTHER DIVIDI NG H EADS Since the last edition of this boo k was printed thr ee new divi din g heads have appeared on th e market. The first. of my

Fig. 39 The George H. Thom as Versatile D ividing H ead

Fig. 37 Steady in use on a gea r cu tt ing operation

Fig. 3 8 Author 's design for simple dividing hea d

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58

59

own desi gn, rep laces that shown in Fig . 35 , lon g out of production after the maker die d sever al years ago. It is essentially similar wi t h detail im provem ents. It has a ta ilstoc k for suppo rt ing long sle nde r piece s, and a pai r of raising blocks which bring the cent re height up to just ove r 3 t in. and t hereby all ow fo r rotat ing work up to the size of the 7 " diamete r Myford face pl ate. It is shown in Fig. 3 8 . The second typ e is a m uch m o re elabo ra t e a n d v e r s a ti le appliance de sig ned by Mr Geo . T ho m as, and suppl ied, like t he first one, by N.S. & A. Hem ingway , 30 Links View , Half A cre, Rochdal e. In this head a 24-ho le divisio n p late p rov ide s for simple dividing w ith thos e factor s associat ed w ith 24. A 4 0 ­ tooth worm w heel and w or m ca n also be engaged, w it h a si x- row dri lled - ha l division plat e, giving mu ch fin er di visions. This plate can be rotated by a subsidiary worm, t hereb y permi tting very high

nu m bers of divisions to be obtained . Most peop le will need some help to m ake t he full est use of thi s device and the book by Geo . Thom as himse lf on its constructio n and use, (Dividing and Gra duating , Ar gus Books Ltd.) will be fou nd t he best source of infor m ation. Th is head is also ava ilabl e with tai lstock and raising blocks, but in normal for m is shown in Fig. 3 9 . The third head is supplied also in kit form by M odel Enginee rin g Serv ices . and was desig ned by Mr Ron Kibbey. It uses sta ndard Myfo rd cha ng e whee ls as division plates, but has a fork ed lock ing plu nge r whi ch can span ov er a to oth as we ll as drop be tw een tw o t eeth. Th us the num ber of divi sions in creases to tw ice the number of teet h in any w heel. In addition it has a mount ing for a w hee l- pa ir to m esh w ith t he spindle w heel. giving a ge ar ratio to add to th e basic divisions. It is not at present prov ided with a tailstock or raising bl ocks. Th e head , w ith ext ra gea r pair in pos itio n, is show n in Fig. 4 0 .

Opposite, Fig. 40 The Kibbey dividing head

61

CHAPTER 11

Dividing Heads and, Gearcutting h ea~

The av ailabi lity o f a di vid ing is again essentia l for doing gearcutti ng on the mill ing m ach ine. Of cou rse the re are types of gears on e j ust cann ot do, bu t ordinary spur gears can be don e perfectly wel l for m od el engi neeri ng purposes . wh ere nei the r high speeds . extre m e silence, nor high rate s of pow er tr ansm ission are dem anded. The design of gear s is a subj ect outside t he scope of this book, which is intended to deal with workshop ope rat ions. but there are plenty of sources of inf orma t ion on gear design . The simp le ty pe of div idi ng head already illu st rate d w ill serve very w ell if the gears to be cu t hav e such a num ber o f teeth as the indexing cha nge w hee ls can deal wi th. Bu t if th e num ber requ ired cannot be go t from exist ing wh eels, t hen a more com plex head such as the M yfo rd. w ill be needed. Fig. 37 shows th is in use cutti ng the teeth of a pin ion w hic h are inte gr al with th e shaft. The blank was turne d to t in. dia met er on the part t o be held and this was gripped in the sta nda rd Myford t in. coll et. w hi le the othe r end of th e com po ­ nent bei ng centred wa s support ed by a 60 degree centre in the ove rarm fitt ing. This picture sho w s the st eady bracke t descr ibed in the last chapter in use. The cutt er is a simple flycutt er in a boring bar

held for co nven ienc e in a bo ring head. It is shown in close- up in Fig. 41 . The prof ile w as establi shed by grindi ng to suit a whee l of the sam e pitch w ith slightly mo re teeth. The variation is so sm all as to be of no im port ance. especial ly as the pi nion ro t at es at only a lo w speed. But if several gears are to be m ade . and especia lly if du plicat es may be w ant ed lat er, it can be w orth whil e to invest in one or more prope r disc typ e gear cu tt ers of wha t is now universally known as th e 'Brow n & Sh arpe' type, because th ey we re deve lop ed by th e famous fir m of Brown & Sharpe in U.S.A. m any years ago. Th ey are of cours e now m ade by Britis h firm s as w ell. and by o th ers all ove r th e w orld . to an accu racy of in tern ational st and ards . far be tter th an anything th at is needed fo r model engin eering , and are prope rly back ed off as w ell as being made f rom high speed ste el. No single cu tt er will properl y deal with all num ber of tee th, so t hey are m ade in set s. ea c ~ cutter dea ling wi th a li m it ed range . and each bea rs an ident ify ing num ber. The range runs as fo llows: No.1 135 to a rack No.5 21 to 25 No. 2 5 5 to 134 No. 6 17 to 20 No.33 5 t05 No.7 14 to 16 N o. 4 26 to 34 No .8 12 and 13

I

III

Fig. 4 1 Close-up of fl ycu t ter and pin ion

Fig. 42 Gearcutting with Brown & Sharpe cu tter

63 62

Fig. 43 Flyc u tting 10 d.p . gearw heel, fron t view

These cutt ers can be bought sin gly at any tim e fro m regular to ol merch an ts and I doubt if any disco unt w ould be giv en for buying a com plete set o f 8. So th ere is no need to go to the expense of acquiring a com plete set unless it is fir m ly kno w n th ere w il l be a use for every one ! Fig. 4 2 shows one of th ese doing a sim ilar job to that depicted in Fig. 37 . The smoother acti on of the mul ti-tooth ed cu tter made it po ssib le to dispe nse with th e use of the ste ady stand. though care was taken not to be too roug h wi th the feed. espe cially at th e st art of each cut. Going now fro m w ha t m ight be called the sub li me t o the ridiculous. or at leas t from th e m iniature to the outsize . the next photograp h shows the cutting of a m uch larger gea r. act ua lly 9 .600 in. p.c.d. This is a gu nmeta l gear needed as par t of a metal patte rn from w hic h the flyw heel of Fig. 20 was made. It is only 3/1 6 in. thick but the

64

t eet h are 10 d.p.. approx. 5/ 16 in. cent res. so qu ite a lot of met al had to be rem oved at each too th. The cutting w as do ne wi th a flvcut ter. grou nd up by hand to match a s i l h o u e tte of a 1 0 d .p . t o o t h i n M achinery's H andbook. using a m agnifier, this cutter bein g set in a boring ba r of rather excessive length in a bo ring head. Tw o cuts w ere ta ken, bu t even t hen there w as a good deal of spring and noise. Th e shape of the bla nk casting wa s arranged to provide for mo untin g by 8 bo lt s on the large Myfo rd faceplat e. (9 in. diamete r! and th is wa s fi xed on the m iller t able so as to ov erhang the side. Tha t pe rm ittgd fixi ng a sta ndard ang leplat e on the table too. just to uchi ng the back o f the facepl at e, which redu ced t he spring iness of that. and provided a back -s top against the da nger of slipping. It w ould have been asking a lot of the single bolt of the divi di ng head to prevent movem ent, und er the co nd it ions

Fig . 44 Fl ycu tt ing 10 d.p . gearwheel, rear view

prev ailing. but using this safeguard all w ent w ell. It is well worth keepi ng in m ind in th e hom e w or kshop th at th is m ethod of back-up is wi dely used in the engi neeri ng in d u stry . espe c i al ly i n t h e h eav ie r sect ion s, on planing m achines and others w here t here is eit her high thrust or hig h im pact,' som etim es both, because it can

avo id damage to m achines and w o rk. as w ell as po ssible injury. Fig. 4 3 show s the front of th e gear disc. and in this view the divid ing head is not visibl e. But in Fig. 44 bo th th e ang leplat e and the dividing head are seen. The gear blank w ould only just swing in the gap of the M yf ord lath e so w ithout raising block s it repres ents about the largest job that can be t urned .

65

CHAPTER 12

Dividing Heads and Tool Making T here are many occasions in tool making w hen divi di ng is nec essary . Multiple edged cutt ing too ls like taps. reamers, m illi ng cutters, cou nte rsinks. et c. all really need divi di ng de vi ces to produce the best results, eve n th ough so me of th e sim ple cutters can we ll be made by filing or free hand gr inding. Howeve r, th e f orm of the teet h or flut es som etim es settles that

rough and ready methods j ust w ill not do. and as in the next exam ple the physical di ffic ulty o f getting at th e metal that has to be taken aw ay mo re or less sett les that m echan ica l divi di ng m ust be em ployed . Fig. 4 5 show s the fl uti ng of a long-thread Acm e t ap which is held in a collet in the spindle of a simple dividing head, using change w heels for the divid in g. In order to

Fig. 45 Flu ting Acm e thread tap

66

obtain the maximum swa rf clea rance this tap has five flutes. The head has no tailstock so the outboard end of t he tap is rested on a pa ir of Picador bloc ks and the clamp rests on anoth er pai r. These are very usefu l acce ssories for mi lli ng opera ­ tions. Of course each tim e that a flute is co mpleted the clam p has to be released bef o re th e wo rk can be rot at ed to the po siti on for the next flut e. A suitable tailstcck. w ere it available, woul d obv iate the need for th is. Th e 5 flu tes are obt ained by mo vi ng 12 te et h at a ti m e on a 60 tooth wh eel. The cutte r being use d is a com m ercial t ap-f luting cu tte r pic ked up cheaply at a sale. These cutters are made w it h a som ew h at lo p- sided ro un d ed prof ile speci ficall y for this duty, but if it had not been available, a flycutt er w oul d have been gro un d up to the profil e of a simil ar tap. The prof ile is not de sperat ely im por t ant and a sm all error wou ld not matt er.

A nother example o f the use of the dividing head, th is tim e cou pled w ith the use of a small rotary tab le, is shown in Figs. 46 and 47 . The wo rkpiece to be produced was a fine too th mill ing cutter with a roun d end for routing or hand m illing on the light alloy cy linder head of a car eng ine. The co mmerc ial ly avai lab le cutters for use in ele ct ric drills had such coarse teet h that once they touched th e surf ace of t he alloy t hey we re uncontroll­ able and pulled sideways so vio lent ly that dama ge to the cylinder head was almost a ce rt ain ty. So as fine pitch cut t ers appea red to be not purchasable it was de cided to m ake one. The bla nk, of a carbo n st eel sim ilar to silver st eel but som ew hat low er in carbon, wa s made to hold in a collet and w as give n a sm all recess in t he end for the flut ing cu tte r to run into. The div idi ng head , with a 50 to ot h change w heel an its spi ndle . was m ount ed on a stee l plat e so that the end

Fig. 4 6 Cu t ting teeth of ball -end cu tter

67

Fig. 4 7 Close-up of ball-end cutter

of th e wo rk- piece w as beyond th e centre of t he rotary t able by half its diam et er. In other w ords , the centre of the ba ll end was ov er t he centre o f th e rot ary tab le. T he axis of the work w as on the rot atio n cent re. This is no t app arent fro m th e pho tog raph, but w as an essent ial feature of the set- up. A sto p blo ck wa s clamped to th e underside of the m illing m ach ine table with a to olmaker 's clam p, visi ble in t h e p ho to g raph , to l i m i t t h e ta bl e move ment po sitive ly to this posit io n. In the other direct ion the mo vemen t of the table brou gh t the cutt er to a pa rt of th e too l shank sm alle r tha n the diam eter at the bottom of the flu te s so th at ind exing could be done w ith th e cutte r in th e clear. The cutter used w as a carbon steel one made origi nall y for producing locom ot ive lubricator ratchet whee ls, w it h a 60 degree single angle. W ith the axis of t he work parallel to the tabl e a cut was started at the requ ired full depth , and the

68

table traversed alon g br inging the cutte r int o op eration cutting along th e cy lindrica l port io n. Wh en the tabl e was arrested by the te mporary sto p block, the rotary table wa s turned by means of it s w or m , so t he dovet ail cutt er co ntin ued cuttin g ro und the ball end of th e w o rk. W hen th e culler ran into the recess, the feed w as reversed fi rst wi th the ro t ary table, then wit h the main t abl e, back to th e st arting poi nt , w her e th e cu tt er w as cl ear of th e w ork sha nk , T he d ivid ing h ead was then indexed one tooth on the w heel. and a new cut st arte d, Eventua ll y all 50 cuts we re co mp leted as shown in Fig. 4 7. The working ' diamete r of this tool is f in. and tlgere are 50 perfect te et h. The too l w as hardened and tem pered, and w hen put to use in an electric dri ll was fou nd to b e ent ire ly sat isfac tory, It worked com ­ pletel y cha tt er-free, wi th no ten dency to run away, and in spite of its fin e and sha llo w t eeth , removed metal at a very

Fig. 48 Gashing fl ut es in large countersinking tool

gr ati fyin g rat e. Th e w ork on th e ports in th e alloy head wa s co mp let ed t o the great satisfaction of the user, leaving a beautiful smooth surfa ce for the gas flo w . An other exam ple of cutting to ol making is sho w n in Figs. 48 and 4 9. A large 60 degree count ersi nk w as need ed for a com mercial operati on on steel tubes, the to ol being about 2 -!- in. diam ete r. It wa s made with an interna l fo rm ide nt ical w it h the M yford lathe spi ndles from a carb on­ ma nga nese ch rom e all o y of known identity, so th at subs equent hardening coul d be done w ith out risk of failure in a co mmerc ia l e s t ab li s hm en t wit h knowledge of th is st eel. In t he pictu re it is sho w n moun ted on the M yford divid ing head hav ing th e flut es cu t wi th a specia l ang le fo rm di sc type cutt er. Beca use of th e pec uliar angl es w hich are invol ved it was necessary to be able to set the head with it s axi s at an incli nat ion to the table, and it proved that the simp lest way to do

this w as to use a vertical sli de. There was qu ite a lot of me ta l to be t aken out of the 25 flutes in this de ci ded ly toug h steel , and as usua l th e cutt ing wa s a lo ng wa y fro m the anchorage point, so the st eady stand was brought int o use at the back of t he head, as it proved too diff ic ult t o set it at the sam e side as t he cutt er. Howe ver, it served quite w ell in th at position and t her e w as n ev er any su ggest ion of insecurity. Th e m ain gashes fo r the flut es w ere taken out first, w ith two cut s dow n each flu t e. Then the head wa s til ted to a new angl e and another series of cuts take n to accomplis h the rel ief. Because of the coni cal shap e of the work the ve rtical slid e had to have it s base set at an ang le to the miller table. A ll th ese appa ren tly co m­ plicated setti ngs had to be established experi mentally (t houg h pos sib ly w ith a lot of effort they mig ht have been calcul at ed) to give the de sired for m of the cutt ing

69

CH A PT ER 13

Dividing Heads and Graduated Scales

Fig. 49 Rear vie w showin g s tea d y stand in use

edges of the count ersink and the rake angles desired in two directions. The sm all division plate in use is one wh ich had been made some ti m e pr eviously for doing 12 5 div isio n m icrometer dial s. for w hic h unfo rt unatel y the st andard M yford plate s do not provide , or did no t at that time. How ever, w ith th is set -up and not too many hours w or k it proved possible with ho me workshop equipme nt to produce a very suitable specia l countersink w hich would inev itably have cost a small fortune

70

if it had had to be made in a com m ercial factory. It is ho ped that th ese exampl es of too l m aki ng wi ll enco urage al l who need non- stan dard t oo ls, and wh o know of no firm th at w ould take them on, or are det erred by the high co st of labou r­ int ensive spe cials. Who kn ow s, somebody in a home works hop m ight t ake on th e job of hel ping out some tool fact o ry that w ould not wa nt to be diverted from its norm al w or k by job s of this kind?

In the co nstructio n of sma ll m achine tools and access ories it is o fte n de sira ble to have grad ua te d sca les fo r the co n ­ ve nience of precise measurem en ts, and the cy lindr ical m icrometer dia l is undo ub­ tedly the com mo nest type . Depe ndi ng on the number of graduation s req uired the eng rav ing or cutt ing of the li nes can be done w ith eit her a simp le head or the worm gea red type . There is a choice be tween usin g a non-rotati ng cutte r of the pla ning or slott ing type, and usin g a rot at ing cutt er like t hose employed on pantograph engraving m achi nes. In each case the work is mounted on th e d ividing head and t he table screw is used t o move the work against the too l. It is advisable to clamp stops to the table . if the mac hine does not have st op devices built in . so as to positively limit the t abl e movement an keep the li nes the co rrect length. W he re there are li nes of mor e than one length on the sam e di al, one or more slip s of she et metal ca n be inserted in front of the stop to obtai n the sho rt lines . The cu tting tool can be gro un d to an included angle of about 50 degrees, Few mode lle rs have access to an engraving cutter gr inder. which is the ideal m achine for grindi ng the D-bit type cutters with conica l end w hich are neede d. but t hey can in fact be ground

on the Quorn g rinde r. w hic h is becom ing more and more popular wi th model engi nee rs. Those w ho do no t po ssess one of these versatile mac hines may have some friend w ho can hel p ou t by grindi ng an occa siona l cutter. For my par t I pr efer the rotating cutte r bu t then I do have the machine to grind them. W ithout this a slo tting tool can easily be ground and if rigid ly held w ill also do a good job, Fig. 50 shows a cy lindrica l scale be ing eng raved on the m ill er w ith a rot ating too l. This is no t a loose co llar, the scale is on the co mpone nt itself. act ually par t of a Quo rn grinde r, but a separate co llar wou ld just be mount ed on an arbor and treat ed in t he same way. Fig. 51 is a close- up of th is operation , Some art icles need the sca le on a flat surface but sti ll in a curve, One of these is needed on the Ouorn gri nder, and Fig, 52 shows this set on a rotary tab le on the miller and being dealt with by a rot at ing cu tte r as the last examp le. The M. E.S. table in the pict ure has a 90 too th worm w heel. so one revolut ion of the worm gives 4 degrees movement and each division on its 16- line micrometer collar gives one quarte r o f one degree , The scale being eng raved is one sp ec ified in degrees, as it is an ang le-setting scale.

71

Fig. 50 Cylindric al ma ch ine com p onent being graduate d

Fig. 5 T Close-up of previous operatio n

72

Fig. 52 Graduating part- circular arcuat e scale on fla t surface

Conic al mi cro me te r collars are som etim es requ ired , but they are more diff ic ult to prod uc e and should be avoided in the desig ning if at all possible. For graduat ing one of these the dividing head woul d nee d to be tilte d aft er th e fashion of th at in Fig , 48. but poss ib ly in the o ther direction. dependi ng on the actua l de sign of the co llar. On e po int in ma king scales of any kind. T he fig uring should always be done so

th at th e figures are the right w ay up as seen in using the scale . The figures m ay need to have risin g value . . . 10 , 20 , 3 0 . . . to the right hand from t he zero m ark, but quite possib ly, depe nd ing on circ um­ sta nces they may need to be the opposite way. It is as w ell t o get this thoroughly sorted out before starting to use ma rking punches to pu t the figures in. because it can be very di fficu lt t o retrieve th e situa­ tion if th e start was made the wrong wa y.

73

CHAPTER 14

Cutter Speeds for Vertical Milling a~

In gene ral I af raid mode l eng ineers do no t have very clear ideas about ho w fast they should run t heir lath es, drills or mi lling m achines. To run t oo slowly extends the w or king time unnecessarily, but to ru n t oo fa st will soo n blunt a cutter and may also cause poor w ork finish through cha tter. The wear on m il lin g cutters (apart from flyc uttersl is quite impo rta nt because of t he trouble of sharpening t hem , and broke n cut ters can be qu ite an expe nse. The pri nciples w hich govern the speeds of cutting metal in othe r mac hines such as the lathe and dri ll can be taken as a usef ul guide, in th e sense t hat any speed which an a particular materia l w ill blunt a lathe tool or drill wil l likewise blunt a m ill ing cutter. But on t he vertical m iller there are other problems too. Generally t he point of cutting is m uch furth er from the supp ort than that of the lathe t ool. It wi ll also be a long wa y co m­ pa ratively fro m the spind le bearings. The work may be m uch furthe r from the slideways than it wou ld be from the bed of th e lathe. Th e cutt ing tool is normally unsupport ed at it s cuttin g end, and it s own elasticity is added to that of the chuck, spindle , work, etc . So speeds which might be feasible on the lat he may well be fou nd much too hig h on the mi ller.

74

As an exampl e, turni ng back to Fig. 2 0 wi ll show how eleva ted the surfac e o f the w or k is f rom the t able slides, and in th is exam ple lo w speed s were esse ntial t o obtai n a reas onably goo d fi nis h. Th e rat es of feed and dept h of cut w hich are co m monp lace on industrial mach ines are quite out of order in the home worksho p. N ot only are industria l machines heavy and rigid, so are the wo rk holding dev ices, and the work it self is much more robust and rigid. Also, and th is app lies particu larly when cu tting stee l, these machi nes can usually flood the cutter with coolant , t aki ng away the heat gen erated in t he cutt ing ope ratio n, and that is no t norm ally possible on m achines in t he ho me wo rkshop . So Table III has been com piled to giv e som e gu idance in the kind of opera tions which have been described in the boo k. It is based on using speeds w hich wi ll conserve the sharpn ess of the cutters like ly to be used. For flycu t­ te rs, commercially made endrni lls . and Brown and Sharpe gear cutters, t he tools t hemselves wil l be properly hardened high speed stee l. Fo r the Woodruff cutters it is based on these being hom e made cutt ers pro duced from carbon stee l or 'silver' st eel (w hich is a carbon stee l with about 1.2% carbon and no alloy) . M o re than one

article in Model Engineer in yea rs past has descri b ed met hods fo r maki ng gea r cutters of the Brow n and Sharpe type. and I hav e some of these myself, mad e from plain carbon st eel of abo ut 1% carbon . Such cutters m ust be run mo re slow ly than the high spe ed steel cutters of com ­ mercial m ake, but it is possi ble that a w ide r var iety of tools w il l in fut ure be ma de in the home w orkshop s, as a bett er understa nding of too l making and th e con ­ t ribution w hic h the vertical m iller can pro vid e com es t o be rec ogn ised . The cutti ng sp eeds t o be used with such tools w ill need to be arranged t o sui t the tool m ateri als and the w ork they are doing. The proper mou nt ing of tools in th e

miller is a matter of grea t im port ance. Reference has already been made to t oo ls which screw di rect ly on t he spind le nose , and anothe r chapter in this boo k w ill give descriptions of the milling chucks w hic h are currently availab le . It will be foun d that some of the m illers at present on offer have spee d ranges wh ich do not go low enoug h to mat ch the botto m end of the recom mended speeds on Table II I. This is un fort unate, bu t it is a fact of life, and one mu st do t he best on e can w it h it, even it it me ans occasional ly bor row ing the use of a friend 's machine. Naturally it w ill t end to in flu ence the decisio n w he n thinking of pu rchasing a machine.

75

TABLE III

TABLE III (continued )

FLYCUTIING . Flat surfa ces as in Fig. 16, H.S .S. cutters, easily sharpened. Dep th of cut : Mild steel .0 30 in. Brass .0 4 5 in. Light A lloy .0 60 in. (inches) Diam eter of cu tt ing : Speeds r.p.rn.: Mi ld Stee l Brass Ligh t alloy

KEYW AY CUTIING. With H.S.S. disc cutter Fig. 26 , or slitting Fig. 23 . (inc hes)

1

It

2

2 l2

3

31

4

4t

5

150 2 30 57 0

100 150 3 80

75 1 15 28 5

60 90 230

50 75 190

45 65 165

38 57 14 5

34 50 125

30 46 1 15

Cutter diameter. Speeds r.p.m . Mild stee l Bras s Light Al loy

2

2t

3

3 2'

4

65 1 15 190

55 95 15 5

45 75 125

38 65 1 10

33 55 95

GEARCUTIING. Commerc ial H.S.S. Brown & Sharpe cutters 2~ in. di am eter. Fig. 42 . Speed s r.p.rn. 48 M ild ste el Brass 80 Light A lloy 11 0

Sp eeds may well be lim it ed by the exten t that sw arf throw n abo u t the workshop can be accepted.

'Hom e-m ade' cutters prod uced from 'silver steel' ,

ENDMILLING . Sp iral fl ute H.S.S. endm ill s. Dept h of cu t up to ~ of cutter d iame te r up to 3/ 16 in., then up to -i- o f diame ter. Wid th of step be ing cut up to } o f d iameter. (inches) Cutt er diam et er 1/1 6 3/32 1/8 3/8 1/2 3/16 1/ 14 5/8 3/4

Cut te r diam eter, Speeds r.p.m .: M ild st eel Brass Light A llo y

Spee ds r.p.m .: M ild steel Brass Ligh t alloy

18 0 0 15 0 0 12 0 0 2500 2000 160 0 3500 30 00 2 500

800 11 50 17 00

65 0 850 14 0 0

450 650 120 0

3 50 450 9 00

2 50 350 800

18 0 250 70 0

KEYWAY CUTIING . H.S.S. spiral flu ted endm ill s or slot dr ills. Fig. 24 . (inches) W idth o f keywa y 1/ 16 3/ 32 1/ 2 1/ 8 3/ 16 1/4 3/8

5/8

3/4

Depth of cut: Mi ld steel Brass Ligh t alloy Speeds r.p.rn.: M ild steel Bras s Light alloy

76

(inches)

1t

1 2t

2

2}

60 120 18 0

50 10 0 150

38 75 110

30 60 90

WOODRUFF KEYWAYS. Using 'hom e- m ade' silver steel cu tters, Speeds increased by one third for co m me rc ial H,S.S. cu tters. (inc hes) 3/8 5/ 16 1/4 Cutter diamete r. Speeds r.p.rn .: 250 30 0 380 M ild steel 450 580 70 0 Brass 800 10 00 900 Light All oy

may be

1/2 200 3 50 650

(thousand ths of an inch)

10 12 15 180 0 2500 3500

15 17 18

25 27 30

1500 120 0 2000 1600 3000 2500

30 40 45

45 60 65

70 10 0 1 10

100 140 13 5

2 00 250 300

2 50 300 3 50

800 11 50 17 0 0

65 0 850 140 0

450 650 1200

350 450 900

250 350 800

18 0 250 70 0

Cast ir on, un less excep tiona lly hard, may be cu t at th e same revs . as mi ld stee l, but for work on carb on stee l ('silve r stee l'). alloy stee ls, and free CU ll ing sta in less reduce revs. by one third. For non - magnetic stain less reduce by half.

77

CHAPTER 15

Work-holding with Difficult Shapes Pro blem s do arise from time to time reg ardin g the m eth ods of holding work in the m illing m achine. In fu ll sca le engi neer ­ ing th ese problem s are not nea rly so acut e as compon ents are m or e solid and clam ps can be app lied w ith out crus hi ng the pieces. Often wi t h model parts it is di ff icu lt to ge t a hold sufficien tly fi rm ly withou t m ore or less mutil ating the piece. One m eth o d I ofte n use bo th for castin gs and bar materia l is to arrange fo r an accurate chuc ki ng piece to be left on the co m p one nt unti l all operati o ns are co m p lete and th en t o rem ov e th is. Gener all y this p iece is m ade to su it one of' the M yf ord coll et s, from t in. diam et er dow nw ards, since the co lle ts do hold the part w it h great accuracy, and after turn ing operations it can be tra nsferred to the miller w ith the coll et pl aced in a di viding head ; even if no indexing has to be done , the head act s as a very effec tive vice. So me times thi n compo nents prese nt prob le ms i n ho ld i ng on th e m ill ing m ach ine. If one sid e is already fl at one can use do ub le- side d sticky ta pe, available from drawing o ff ice supply shops and so me stationers. If tw o or three strips can be used , an astonishing ly firm grip can be obtained, w hich w ill stand up t o shea r forces induced by m illing. I have also in an

78

industrial p lant stu ck down m et al which had to be to oled all th e w ay ac ro ss th e p iece, on a fal se base w ith woodw ork er's glue and a sheet of new spaper. A fte r the operation s are comp let ed a fine chisel is knocked in betwee n the part s and the pape r t ears w ithin its thick ness, so th e pieces come apa rt wit h some pap er st icking to each . This can th en be washed off w it h hot w at er. Th ere is not hing very orig inal abo ut t his, of course, it is an age­ old pa t ter nrnakers' m eth od of pro duc ing a patt ern wh ich has eve ntua lly to be in hal ves , but it is a sound me t hod not nea rly so well known as it sho uld be. Fig. 5 3 shows a light alloy casting being faced rig ht across w it h a flycutter, th e cas ting bei ng stuck to the t able wi th sticky tape and no th ing else. How ever, t he var io us exampl es give n throughout th e book shou ld serve to show how to undert ake a really wide range of jobs . A t the risk of seemi ng repe titive I would agai n st ress th at it is often wort h w hile to m ak e a ji g fo r hol din g or loc ating th e work , j ust to m ake sure it can be held fi rmly enoug h without da mage in the rig ht attitude . The ki nd of ji gs and fixt ures neede d in m od ellin g seldo m involve mo r t han a few mi nu tes or pe rhaps an hour to make, and if this safegua rds the co mpo -

Fig. 53 Tape- held w orkpiece being fly cut

Fig. 54 Three-face ang leplate used to align vee-b lo cks

79

CHAPTER 16

Milling Chucks for Safe Cutter Holding

Fig. 55 Three-face ang lepla tes used as m ain p acking

nent , as w ell as t he tool s and m achin e. it is ti m e we ll spe nt. If a duplicate co m po­ nent is ever neede d that w i ll be produce d exp editiously w it hout risk t oo. A n gl eplates A new type of anglepl at e has been int roduced by Hemin gw ay. This has three faces m achined at 90 degree s to one ano the r. I have found over many years th at cast- in slot s in ang lep lates never seem to be in the righ t place fo r any job, and it seems bet t er to just drill a hole wh ere it happens to be needed. Th ese

80

an g l e p l a t e s , wh i c h a r e sent out unm achined in lig ht alloy, are in three sizes very conve nient for use in ho me wo rkshops and can easily be faced up on the M yford lathe bo rin g t able o r faceplat e. Fig. 54 show s on e of th em set across a mil ler tabl e t o locat e the tw o vee-block s in w hich th e w ork is resting. Fig. 55 show s anot her pai r used as main packing s w it h Picado r st epped blocks o n t op t o give th e last bi t of heigh t adjustme nt for the cl am p pl at es. So many sizes are ava ilab le by selecting di ffer en t atti tu de s of the se blocks tha t they are very useful indeed.

Th e newcom er to ve rtical milli ng m ay wo nde r w hy there should be any need for special ch ucks for m illi ng cutters, and especially w hen he sees that these are fairly expensive accessorie s. may be tem pte d t o make do w itho ut one. But first of all it is nece ssary to realise th at t he force s acti ng upon m il ling cutters in use are generally quit e diff erent from those act ing on dr il ls in a drilling mach ine or lathe. The drill is usually subject ed, except at the mo m ent of com plet e pe net ration , to axial fo rces on ly , whi ch press it mo re and m ore firmly in t o t he M orse t aper hole in the spindle. Eve n if it is held in a drill chuck and has a para llel shank, t he sam e thi ng applies. But th e m illing cutt er is subject ed to transverse for ces, across th e axis , and unless it is screw ed on the spindle, these forces have a co m p on en t wh ich is pressing against t he inside of the Morse tap er hol e, and thereby try ing to cau se the cutter to slide out of the spindle . Each ti me t he spindle rota te s the pres sure is transferred to the opp osite side of the hol e. and this waggles the tool out of the spind le. So fi rst of all , any tool mounted by a t aper shank, whether it is a ch uck or a solid endm ill w ith taper shank, MUST be

pro vided w ith a drawba r through the spindle to stop th is ten dency to w ork out. For cutt ing tools w hich in ope rat ion prod uce no end forces that precau tion is suff icient. But all th e spiral fl uted end m ills and slot dr ills do gene rate end forc es, tending to screw t hem out of th e holding device. (Strictly speaking this app lies to cutt ers w ith righ t ha nd rot at ion, like a drill, and right ha nd f luting , also like a drill. But as it w ould be rem ark able for any othe rs, tho ugh m anuf actured, t o be fou nd in a home wo rkshop , the others can we ll be disregar ded.) So spiral flut ed cutt ers w ill try t o work ou t of a chuck, if parallel shanked, and m ust be fo rcibly prevented. It is not good eno ugh to ho ld th em in a thre e-jaw lathe ch uck, especiall y since mo st of th ese exert mo re pr essure at t he in ner end tha n th e out er, through wear existing in the jaw slides, in eff ect givi ng them a slight t ape r. This is w here th e specially des igned mill ing chuc k com es int o its ow n. Th ere are tw o bas ic types, but each is arranged to grip the cutte r firm ly on it s paral lel shank by a split coll et clo sed by a screw thread forcin g the collet into a conica l part of the chuck. In addition one typ e uses cu tt ers formed with a specia l shap ed end ,

81

Fig. 5 6 Clare milling chuck

and the ot her typ e uses cu tt ers w it h a sho rt screw th re ad at t he end of t he shank. The first of these, the Clare, has a rect angular end fo r the cu tt er, and this end is undercut by m illing. After passi ng it through a rect ang ular slo t in the co llet, the cutter is turn ed t hro ugh a sm ail angle, so the pa rt not und erc ut overhangs the end of the co ll et, and cannot slid e out. The

collet is no t only retained in the ch uck body by all int ernal ly screw ed ca p w hich fit s on t he bo dy , b ut is also closed on the shank by it. The co llet screw s int o anot her th read in t he cap, which en sures that it lo osens wh en requi red, a sm all span ner being prov ided by the m akers for t his pur pose. This type of chu ck w ill in fact hold cu tters w hi ch do not have the 'tee'

Fig. 5 7 Clar kson milling chuck

Fig. 58 Osborn m ill ing chuck

end, and have jus t a plai n rou nd shank, though of cou rse the security feature is then non-exist ent . But f or sm all cutt ers and light duty it w ill serv e very we ll. The other type of chuck, m ad e both by Clarkson and Osb orn , uses only a screwed shan k typ e of cutt er and can not be used exc ep t w ith this. Th e screw th read on th e shan k, w hen subjecte d to the torque necessary to dr ive th e cu tte r, prov ides the force t o clos e the collet and th ereby gr ip the t ool shank. A cent re device inside t he bod y engag es w it h t he cen tre dimple in the end of the cutt er to reduce fr ic tion force s that w ou ld hamper rot ation of th e cutte r. T h e Cla rkson chuc k needs a spanne r, provided w it h th e to ol. to release t he co llet for chang ing cu tt ers. T he Osborn e uses a finer thread on t he sec ur ing sleeve . t oget her wi th some lost motio n provisions. and can be re leased by

82

hand w ithout th e use of a span ner. There is provision w ith each of t hese for using 't hrow - aw ay' cutters, w hich are m ade cheaply in sizes up to :l- in. These have a plain shank. unsc rewed, of in . di ameter w hate ver the size of th e cutt ing portion. w hich has a sma ll flat in one place . They are set in an adapto r w ith a sm all screw at the sid e, w hic h bears on the fl at , and t his is suffic ient to preven t t heir working out of the chuck. The id ea of th ese cutt ers is tha t they are m ade so cheaply that in a com­ m ercial eng ineeri ng shop it wi ll co st m ore t o re-sharpen one th an to rep lace it by a new one . Whe ther or not t hat is really true will depend on t he par t icula r establish ­ ment in w hich they are being used, bu t in the hom e worksho p, if the re is a Qua m grinder. it will be feasible t o re-sh arpen the m at a wort hwhile cost in tim e and t roubl e, for a w hile , until a cert ai n amo unt

t

83

of shortening has taken place . All the cutte rs with screwed ends to suit the Clarkson and Osborn chucks have Whitworth form threads 20 pe r inch irrespective of diameter. On in . shanks this conforms to B.S .W . and on t in . shanks to B.S.F . fo r both of which dies can be readil y obtained . But fo r other diameters, if one needs to make a special cutter in the hom e workshop. screwing a shank 20 threads per inc h is no t a difficult task. Making the specia l ends for the Clare cutlers is not quite so easy in my view. but the Clare chuck has t he advantages of a sho rt overhang and a sm aller diam et er of body, This is part icula rly useful when holding wo rk in a 3 or 4- jaw chuck on a dividi ng head , when some times it is difficult to clear th e chuck jaws. But all

t

84

these chucks can be fu lly recommended as be ing good precision tools which provide complete security agains t cutte rs worki ng out in use. If an accident of tha t kind happens due to not having a security chuck. a spoiled component is certa in, a broken Culler is possible. and I have seen this happen on a nu mbe r of occasions, So do be w arned , and don' t think the cost of a proper chuck is too high to face. Pho t og rap hs of the t hree chucks men tion ed are shown in Figs. 56 , 57 and 5 8 . The Clarkson Autolock chuck shown here, as we ll as in pictures in the tex t, is fitt ed w ith a damping ring . A fter the chuck is fixed in the Mo rse taper, this ring can be scr ewed up to cont act the end of the mach ine spindle, giv ing extra support aga inst vibrati on.

A RNO LD T HRO P wa s an apprentice the n an Outside Erector w it h the fam ous engineer s Cole. Marchent & Mo rley. Brad ford. Yorks. Produc t s : compound engines to 2 50 0 hp , Uniflows t o 15 00 hp. Diesel oi l engines, condensers for largest pow er stations. Lat er he held t echnica l­ adm inist rat iv e po st s i n hig h - t en sio n swi tc hqear. mi ning m achin ery . st ainless fabrication. mac hine tools, and m arking devices. A t his retireme nt he was th e Dir ector of Engineering, Ed w ard Pryor & Son. Sheffield. He has been an I.Me ch .E. in mo unting seniority over 50 years, serv ing on several com m itt ees and one of B.S.1. He has read pap ers t o I.Mech .E. and the Newco me n Socie ty of w hi ch he is a mem ber. H e has worked for half a doze n years as demon­ st rator on the W orkshop Stand of S.M. E.E. at M od el Engi ne er Exhibit io n s, con­ tributed articles to Model Engine er fro m 193 2, and having been in Sheff ield S.M .E.E. from 193 7 has been it s Presi­ dent fo r. some year s. Founding Dore Engineering in 19 63 . he redesig ned Edgar Westbury 's ve rtic al m ille r and sold it as th e Dore-Westbury unti l tra nsfe r t o Mod el Engin eering Services in 19 7 1. His present interests are sta tion ary eng ines. wo rkshop equ ipment , gardening and ph ot ography. The author

86

87

Index Abwood m illin g attac hme nt 12 Amo lco m i ll i n g atta c h m e n t a nd machine 21 A ng leplat es 80 A ng leplate used as backst op 27 , 29 Arbors for sli tt ing saw s and disc cu tters 35 As tra m illi ng machin e 22 Boring operation s Bori ng heads

45 30

Chuc ks, Clare, Clarkson, Osborn Clutch teeth Connecting rods Crosshead slides , engine bedp late

82

Divid ing heads . de s cr iption principle Plain typ e. change whe el indexing Myford w orm -geared type Use of div ision plat es Use of locating blades Packing block for centre height Steady stand for extra rigidity Dividing head s and gear-cutting Plain type Pin ion cutting Large gea r cutti ng

88

55 43 30 an d 54 55 57 57 57 57 56 62 62 62 64

Divi ding heads and graduated scale s Planing/ slotting and rotating too ls Tabl e stop s and li ne length co ntrol Cutti ng/engraving cy lindrical scale Cutt ing/ engraving flat arcuate scale Con ical m icro m et er dials M arkin g fig ures of scales right way Divid ing heads and tool-m aking Fluting screwin g t ap Cutt ing fine tooth m il ling cutter Cutting large co unter sink Specia l di vision pla te. 2 5 hole D-b it fo r hol e cen tri ng to start dri lls Dor e-W estbury m ill ing m achin e End-ro undi ng : Filing coll ars and rollers Using rotary tab le Fittings for rot ary table Rounding engine cranks Direc tion of table rotation Lo ck ing pre c auti on s f o r ex te rna l work Engine bedpl ate bearing jaw s Engi ne cyli nder solepla te Evolut ion of ver t ical mi ller Flut ing op era t ion s. locom ot iv e rods, cor rec t f lut e form Rods for Briti sh engines Rod s for Ca nadian and Am erican engines

71 71 71

72 73 73 73 66 66 67 69 70 47 14

52 52 52 52 52 53 33 30 12

44 43 43

89

Flywh eel (in halves) joint face Gear cutt ing Grinder for engraving cutlers and bits

31 62

o­ 71

Identi fication of cutte rs etc . by mark ing whe n made

42

J ig-boring : Meas uring by table screws Wri tten recor d of m easurem ent s Example of beam for model eng ine Trip gear lever of model eng ine Boiler tube pla tes Avoidance of back-l ash erro rs J igs for milli ng opera t io ns

46 47 47 48 48 46 78

Keyways for pla in sunk keys: Endmilling feather keyways on plain shahs Keyways on taper shafts wi th tilti ng angleplate Disc cutter milling of keyways Locti ting for permanent assembly Long com pone nts, holding problems Machi ne specifica tions. tab le of M axim at milling attachme nt

90

37 38 41

27 38. 49 24

22

Me ntor mi lli ng ma chine Mill ing cutters. mu lti -tooth : Early (19 th century ) 'fil e-cut' cutters Facemills Endm ills Slitting saws Disc cutters Woodruff cutt ers Brown & Sharpe cutters Tap flut ing cutters A ng le cutt ers M illing cutters, single toot h : Flycutters Connecti ng rod fluting cutt er Profi led gear tooth cutte rs Engraving cutters Milling operation s: Flat surf aces parallel to table Flat surface s square to table Slitting and cut ti ng Com ponent flut ing Tool fluting End rounding Gear- cutti ng Keywaying W oodruff keys and keyw ays Bor ing J ig-boring

22 12

30 38

35 40 40 62 67 69 27 43 62 71

32 34

35 43 67

52 62 39 38

45 46 91

Profili ng Engraving Myford-Rodn ey m illi ng attachm ent and m ach ine Myford co llets Myford dividing head Profiling : Circular arcs Locomotive frame s Sm okebox and cy linder saddl es Pad-bolts Sma ll ar c s d er i ved f rom c u rve end mills Quo rn grinder for tool sharpe ning Quorn gri nder , parts of

92

49 71 21 62 57

49 49 49 49 of 51

83 35 ,71

Rota ry tab les Rotary tabl e. M.E.S.

52 52

Senior milli ng m achine Security of m ill ing cutters : Forces act ing upon drills and cutters Use of drawbars in machine spindles Positive lock ing of screwed cutters in ch uck s Posit ive locking of Tee cutters in chucks Slitting and cutting operations Speeds of m illing cutte rs

22

Tapered sections Throw-away' cutte rs Twin mil ling mach ine

29 83 22

Vic es. use of tw o tog ethe r

27

Westbu ry, Edgar T. Westbury m illing m achine Woodruff keys and keyw ays Work holding fo r difficu lt shapes: Use of chucking pieces lat er discarded Sticky tape fo r t hin art icles Glue and paper for t hin articles Specia lly made jigs for di ff icult shapes

14 14

38

78 78 78 78

81 81

82 82 35

74 93

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WOR

1. Hardening. Tempering and

Heat Treatment Tubal din 2. vertical Milling in the Homo Workshop Arnold Th rop

J . Screwcutting in the Lathe Milflin Cleeve 4 . Foundrywork tor the Amateur B. T. Aspin 5. Milling Operations in the Lathe Tubal Cai n 6. Measu ring and Ma rking Meta/~ Ivan

II I~I3I II'9525 I I ~ 1 ~11001 1 1 1117696 1 1 1 1 1 , 1~11 1 ~ 1 W illi 6

HO PRACTICESERIES

LdW

7. The Art of Welding W.A. Vause

8.

heet Meta! Work

15. Workholding in the i.athe Tubal Cain 16 . Electric Motor" V.1. Cox 17. Gears and Gear Cutting

R.E. Wakeford

9 . Soldering and Brazing

Tubal Cain 10. Saws ami SawlI1g Ian Bradley

I. Law

18. B""ic Benchwork Les Oldridge

1 I . Electroplating I. Poyner

12.

onn«

19. Spring De'ign and 1\t.mutocture Tubal ain 20 . Mt't,l/work and Mac hining

is» ,md Dies

Tubdl Cain I J . Wor kshop Drawing

Tubal Cain 14 . Mak ing mall Workshop Tools

Hint and Tip« Ian Bradley 21. Adhes ives and Sea lants Da vid Lamm as

S. Bray

2. Vertical Milling in the Hom W orksho The increasing appearance of vertic, I mil lin g machines in model engineers' and other small workshops has brou ght the versatilit y of thi s type of machine to the notice of a large and growing group of pot ntial users, but until the fi rst edition of the book wa s publi shed in 197 7 there w as little easily available guidance for the average am ateur or small user. This third , revi sed ed itio n incl udes descriptions of many of the very w ide range of op erations possible, wi th photograph ed examples, plus infor­ mat ion on machines, acce sories, cutters, chucks, r quirement s and methods of work-holdi ng. Arnold Throp enjoyed a long and successful engine ring care r starting with very larg steam and oil engines and including high tension sw itchgear, mining machinery and machine tool s. He has a hi eved over 55 years' membership of the Institute of M echanical Engineers.

ISBN 0-8 5242-843-X

I £6.50 net UK

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9 78 085 2 428 436