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Myford Dividing Head Attachment Manual

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Myford Dividing Head Attachment Manual

Text of Myford Dividing Head Attachment Manual


Theory Since, J-n order to make the fullest possible use of the attachnent, the theory nust be thoroughly understood this is deaft with first. As stated on the chart the ratio of the worm wheel to the worm is 60:1. Ttris neals ttiat 50 revol-utions of the index crank which operates the wonn are required for one revolution of the spindle. For four divisions, for example, we should need a quarter of 50, that is, 1! revolutions of the index crark per division. A^ = Ihat is fr 15 .t 50 is ttre rconstantt for the attachnent. 4 was the nunber of divisions required. lJ is the nunber of revolutions of the index c rank (i.e. each division.

of the worm) required


T o t ak e

an e x a m p l e fro mav

th e

c h a r t;

suppose that

9 divisions

are required.






R e f e r r i n g t o t h e t o p l e f t h a n d c orner of the chart w e see that on the No. t plate it is only the ci-rc1e with 45 h o l e s w h i c h i s d i v i s i b l e b y 3, though on the No. 2 plate +? is also divisible by 3. Either of these could be used. ConsiderinE the former, however, we getl . a

5o 9




.10 rtherefore, require 45 hole circle. compl ete revol uti ons of th e index

F or eac h d i v i s i o n we shall, crank plus JO hol-es on the

It will be obvious that although the chart only goes up to l-OO there wiII be many numbers above this which can be directly obtained from the stand.ard plates. Consider L24 divisions



L5using this r we require to

TLre No. 2 plate 'has a circle having JI holes so that, advance the index crank 15 holes for each dj-vision.

It will be realised that a further rarlge of divisions carr be obtained prepared to make extra plates. Take for exanple I44 divisions


the user is




None of t he p l a te s h a s a c i rc l e w i th L2 hol es, nor any number di vi si bl e by L2, but a plate having this number could readily be made. It i l ayr how ever, be consider ed wor t hwhile to h a v e 2 4 h o l e s , s i n ce thi s w oul d enabl e 288 di vi si ons to be obt ained in the event of the latter being required, at a later date.

The sector arms The two arns of the assembly are secured! one to the other, in any required setting by a slotted screw. The whole assenbly which is noulted on the worm shaft bracket so that, whilst it can be readily rotated as is retained in posltion by friction, settings. the di"viding operation progxesses, it is fi-rmly held in the inCividual Where the rnovement of the index crank is less thal about two thi-rds of a revol-ution (see exanple for 124 divisions per division above) or a whole nunber of revofutions (see plus a portion of a revol-ution less than about two thirds of a revolution chart for 2l divisions) the movenent of the phurger on the lndex crank will be between the arms.W her e t he a rc o f m o v e me n t of the index crank exceeds roughly two thirds of a revolution o r a n u m b e r o f fult turns plus more than about two thirds of a revolution roverf the sector arms (see chart for L6 divisions). t he plunge r w i l l o p e ra te Setting A. the sector arms


between t n e a r m s \ e . 8 .


25 divisions).

Morurt the No. I division plate wi-th the numbered holes to the top. Adjust the settlng of the index crank so that the plunger wi}l drop into the holes in the Open out the sector arms so that there is about 1E0- between them. 45-hol-e circle. 1'/ith one arm (caII this arm a) to tne }eft of the numbered hole and the other arn (call- this arn B) at about 14 o'cfockt-rotate the crank clockwise untj-l the pl-unger clockwise tmtil Next, rotate the secffi-artns will drop into the nurnbered ho1e. arn A is touching the left hand sid.e of the plunger and arm B is at about 15 orclockt. Unless it is already free, sl-acken the screw which clamps the two arms together. Starting at the hol-e to the g!g![ of the pfunger count 18 holes in a cfockwise and, holding arm A firmly against the l-eft hand side of the plungerr move direction arm B anticlockwise until- ibs inner edge lines up with the lower edge of the f8thhole and tighten the screw to lock the sector arms together. there should be a total of L9 holes between the sector arms). (N.B. (Ili-E. 1) In this example

Fig. I





Operation over the arms (e.g.

15 divisions).

Open up the sector arns so that there is about 12Oo between them. Adjust the setting of the index crank so that the plunger will drop into the holes of the .,2-t1o]'e circfe. With arrn B to the right of the numbered hol-es and -(No. t plate). arrn A at about 18 orclockr rotate the crank cloc -wisE-TI-[ the plunger will drop into the nunbered ho1e. Next rotate the seffii arms anticlockwise so that arm B whichistotherightofthep1ungeristouch1ngit(s-tirrontnerlghthaadside). Starting at the hol-e to the left of the plunger cor.nt 8 (i.e. 32 - 24) holes j-n al anticlockwise and, holdlng arm B firrnly against the right hald side of the direction pfunger, move arm A upwards, in a clockwise direction until its upper edge lines up with the lower edge of the required hol-e and tighten the screw to lock the sector arms together (N.B. In thi.s exampl- there wil-l be a total- of ! holes between the e s e c t o r a r r n s) . ( F i g . 4 ) MountinR the attachment. Where circumstances permit and both sfides are availabfe it will generalfy be fould preferabl-e to use the plain vertical slide 67/f as thj-s wil-l give greater rigidity. In addition, the maximun height of attachrnent splndle above the headstock spindle is greater than on the swivelling slight1y slid,e 68/2. l{hen working with the axis of the attachment spi-ndle parallel to the axis of the headstock spindle it will generally be preferable to have the attachment spindle at the same height as the headstock spindle, thus working on the horizontal centre fine. ldhen using a cutter on an arbor between centres, with the axes of dividing attachnent and headstock spindles at right angles one to the other, if the sun of the radli of cutter and work exceeds 2.I/8tt (e.g. a 2rr dia, cutter and a 21tt d.ia. component) the attachment nay be raised z.I/Btt by using No. 3O/OLI block for ML7 dividing and Super 7 lathes. Where this is not available, or if when using i-t, the sum of the radii exceeds {tt, it wilf be necessary to increase the centre distance between cutter and work i"n some other way. fhis may be achieved by repositioning the key in the back of the spj-nd1e bxacket by fitting i-t in to the vertj-cal slot and rotating the table of the swivelling slide 58/Z ana rnounting the attachment wlth the slide so swivelled that the attachment spj-ndle 1s looking up at an angle. The axis of the feedscrew of the miUlng slide (See w1ll- then be paral1e1 to the axis of the spi"ndle of the dividing attachmen';. drawing on sheet 5.25468). Ttre appro'ximate setting for height may be made with both cutter and workpiece in position by rotatlng the sfide table and dividing attachment ald sinu-l-taneously advancing or withdrawing the cross slide, and, by means of its feed screw, adjusting the positlon of the milling slide tab1e. The feed of the workpiece across the cutter will be by rneans of the feed screw of the swivelling sl-ide, the depth of cut wifl be controlled by the cross sl-ide feed screw. It will be noted, however, that the depth of cut actr.rally applied will be less than the movement of the cross sl-lde and that the relationship will vary withd i ff6'i hm rhdl ^c

The amount of cross sLide novernent for by using the formulaSinA Where f c A = = =

any required

depth of cut nay be cal-cu-l-ated

a mo u n t c ro s s s l i de i -s to b e m o v e d re q u i -re d d e p th o f cut and di vi di ng a n g l e o f i n c l i -n a t i on of sl i dc

attachment t he

Ref er enc e to tri g o n o me tri -c of 30" to t he ta b l es w i l l show that an i ncl j -nati on si nce the amount of movenne nt of hor iz ont al s h o u l d b e c h o s e n w henever possi bl e depth of cut. be exactlv twice the reouired cross slide will


Uhere the workpiece is suitabfe it should be nounted in a chuck or No. 1OJl co11et with 14rB nosepiece. It is not advised. that the work be normted between cen!r:e6. Ttie outboard support is not intended for this purpose. Conponents which are bored shoul-d be mormted on a stub arbor nachined to suit. This in turn nay be mounted in a chuck, in the No. 1Ol1 coll-et or it nay have a No. 2 H.T. shalk and be mormted direct i"n the taper in the spindle of the attachment. TLre overarm and outboard support centre. If the component has a centre at its outer end or is mounted on a stub arbor with s u c h a c e n t r e , t h e o u t b o a r d c e n t r e m a y b e u s e d for additional support. Operatlon indexing. of the teeth on a 25 tooth spur gear. tailstock

As am exanple of use, assume the cutting l'lount the cutter support ) .

on ai arbor between centres

(or held ln the chuck, with


ount the vertical slide on to the fathe ald nount the work piece.

cross slide,

the dividing


on to

Centralise the work piece to the cutter ald set for height touches the periphery of the work piece.F it t he nu m b e r I d i v i s i o n p l a te des c r ibed a s A o n s h e e t 2 1 4 6 F . and set the i ndex crank

so that

the cutter


and the


arms as

Set for the required

depth of cut.

Rotate the index crank clockwlse until the phmger drops into the nunbered hole. (N.B. It rnay be found convenient when rotating the index crank to stop just short of the required hol-e and then to tap the index crark round until the plunger drop6 in). ldake the first cut. the left a1low the clockwise plunger to

(arm A touching Check that the sector arms are in their conect position haad side of the plunger) and wj.thdraw the plunger. Rotate the knob to shallow notch to engage with the stop peg. Now rotate the index crank plus 18 hol-es that is up to arn B ald aliow the two complete revoluti.ons (S.2545B Fig.Z) drop in to the hole in the index plate. Cut the second tooth. Rotate the sectorUithdraw the

arms cl"ockwise so thatand i-ndex as before.

arm A is again touching

the plunger.(tr,ig.r)


When operatj-ng over the sector arms (e.g.16 divisi-ons, see sheet 5.2545C), the m ov em ent s o f th e i n d e x c ra n k w i l l agaj -n be i n a cl ockw i se di recti on, thoug h t his H ow ever, & t the connencem ent , t im e t he se c to r a rn s w i l l b e m o ved aati cl ockw i se. with the plunger in the nlmbered holf,arm B will be touching the right hand side of the ph:nger, whereas arm A will be at f nire o t clock | . fhe movement of the index crank wil-l be : -

Withdraw the plunger, rotate the index crank clockwise three complete revolutions p l u s 2 4 h o l e s , t h a t i s j u s t over arm A. Before the next movement of the index crank rotate the sector arms anticlockwise so that arm B is in contact with the plunAer.

N.B. If two or more cuts are to be mad.ein achieving full depth, the f irst , roughingt cut should be made right ror,md the blank before adjusting for depth for the subsequent cut(s). Then operating, always rotate the index crank clockwise.

:If you inadvertently Go back well pa*it

go beyond the requir.ed hole do not cone directly baik to it. so that you can again cone up to it in a clockwise direction.

The bore for the nain spindle of the attachnent is split, the resuJ.ting slot being fitted with a packing piece. $ris is so relieved that the centre screw ca.rr be used, if required, as a locking screw for extra rigidity during actual nachining. The tr"o outer screwe are for bearlng cleara::ce adjustment ald, having been carefulJ-y set during naaufacture, should not nornally be touched.




[email protected] adjus t me n ts am ount of u s e . s h o u l d b e n e c e s sary r" mti l the attaohment has had an appreci able fh e re a re , h o w ever, four w hi ch can be made. it w i l -I be

need adj ustment, S hould t he s p i n d l e b e a ri n g c l e a rance eventual l y nec es s ar y to re mo v e a n d th i n th e packi ng pi -ecen

Erd float iI the spindle can be eliminated by adjusting the collar at the rear end Ihis is threaded (right hand) on to the spindle and is secured of the spi-ndle. by neans of a grub screw which must be rel-eased for the adjustnent to be made ald retightened afterwards. Backl-ash between wonn arrd wormwheel car] be el-iminated by xel-easing the hexagon head screws vhich secure the worm bracket to the nain body of the attachnent and Note that the bracket is keyed to the body. the bracket. The position of the phurger in the index crank can be adjusted if, with the plunger located so that the stral-Low notch is engaged with the stop peg, the ph.urger will not pass over the sector arns (aflow about IA6n, To adjust, 1.5 nn, clearance). release the socket set screw in the end of the pl-unger knob, release the plunger5 in order to reduce the l-oad on the spring, but hold the knob so that the plunger is not fully engaged with the dividing plate and screw the plunger into the knob the requisite anormt. Re-tighten the socket set screw to lock the plunger in positlon in the knob. SUPPLEMENTARY 0HART COVERTNG NUI4BERS FROMl-01 to 200Si-nce the denorni-nator of the fracti-on in the colurnn headed ilTURN INDEX CRANKfTis t he num be r o f h o l e s i n th e i n d ex ci -rcl e requi red, an entry has onl y been m ade in the colunn headed ffINDEX CIRCLE|T if a plate havi-ng this number of holes has to be A blank space in the column headed TTTURN made. INDEX CRANK|Tindicates a number which cannot be obtained either directly or indirectly.


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puerexeg ctncues MYFORD 97"83:73:67:61:27 prvlgJNc AITACHMENTIYORM AND WHEEL RATIO :- 6O/tPLATES 3 ANp 4 ARE S-UplL.lEp AS EXTRA




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