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MTIORD 1495 DIVIDING ATTACIIMEM 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. of the worm) required for each division.
To take an example from the chart; suppose that 9 divisions are required. 6o = 9 a v T= r 2 3 Referring to the top left is only the ci-rc1e with 45 hand corner of the chart we holes which is divisible by Either of these could be see that on the No. t plate it 3, though on the No. 2 plate used. ConsiderinE the l . a +? is also divisible by 3. former, however, we get .10 r .2 "3 5o 9 20 7 For each division we shall, crank plus JO hol-es on the therefore, require 45 hole circle. complete revolutions of the index 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 5o L5 Tfr=3r TLre No. 2 plate 'has a circle having JI holes so that, using this r we require to advance the index crank 15 holes for each dj-vision. It will be realised that a further rarlge of divisions carr be obtained if the user is prepared to make extra plates. Take for exanple I44 divisions &5 = 1+4 12 None of the plates has a circle with L2 plate having this number could readily worthwhile to have 24 holes, since this the event of the latter being required, holes, nor any number divisible by L2, but a be made. It ilayr however, be considered would enable 288 divisions to be obtained in at a later date.
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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 is retained in posltion by friction, so that, whilst it can be readily rotated as the di"viding operation progxesses, it is fi-rmly held in the inCividual settings. Where the rnovement of the index crank is less thal about two thi-rds of a revol-ution per division (see exanple for 124 divisions above) or a whole nunber of revofutions plus a portion of a revol-ution less than about two thirds of a revolution (see chart for 2l divisions) the movenent of the phurger on the lndex crank will be between the arms.
Where the arc of movement revolution or a number of the plunger will operate of the index crank exceeds roughly two thirds of a fult turns plus more than about two thirds of a revolution roverf the sector arms (see chart for L6 divisions). Setting the sector arms A. Operation between / tne arms \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 45-hol-e circle. Open out the sector arms so that there is about 1E0- between them.
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 will drop into the nurnbered ho1e. Next, rotate the secffi-artns clockwise tmtil 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 direction and, holding arm A firmly against the l-eft hand side of the plungerr move arm B anticlockwise until- ibs inner edge lines up with the lower edge of the f8th hole and tighten the screw there should be a total of to lock the sector arms together. (N.B. In this example L9 holes between the sector arms). (Ili-E. 1) Fig. I Fig.2 Fig.3 Fig.4
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B. 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. -(No. t plate). With arrn B to the right of the numbered hol-es and 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 w h i c h i s t o t h e r i g h t o f t h e p 1 u n g e r i s t o u c h 1 n g i t ( s - t i r r o n t n e r l g h t h a a d s i d e ) . Starting at the hol-e to the left of the plunger cor.nt 8 (i.e.
32 - 24) holes j-n al anticlockwise direction and, holdlng arm B firrnly against the right hald side of the 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- e there wil-l be a total- of ! holes between the sector arrns ) . (Fig. 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 slight1y greater than on the swivelling 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 dividing attachment nay be raised z.I/Btt by using No. 3O/OLI raLsi.ng block for ML7 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 w1ll- then be paral1e1 to the axis of the spi"ndle of the dividing attachmen';. (See 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 with d i f f 6 ' i h m r h d l ^ c The amount of cross sLide novernent for any required depth of cut nay be cal-cu-l-ated by using the formula Where SinA f = amount cross slide i-s to c = requi-red depth of cut A = angle of incli-nation of be moved Reference to trigonometri-c tables will show that an inclj-nation of 30" to the horizontal should be chosen whenever possible since the amount of movennent of the cross slide will be exactlv twice the reouired depth of cut. slidc and dividing attachment
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a 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 such a centre, the outboard centre may be used or is mount ed on a stub arbor with for additional support. Operatlon indexing.
As am exanple of use, assume the cutting of the teeth on a 25 tooth spur gear. l'lount the cutter on ai arbor between centres (or held ln the chuck, with tailstock support ) . ount the vertical slide on to the fathe cross slide, the dividing attachnent on to it ald nount the work piece. Centralise the work piece to the cutter ald set for height so that the cutter just touches the periphery of the work piece. Fit the number I division plate and set the index crank and the sector arms as described as A on sheet 2146F. 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. Check that the sector arms are in their conect position (arm A touching the left haad side of the plunger) and wj.thdraw the plunger. Rotate the knob to a1low the shallow notch to engage with the stop peg. Now rotate the index crank clockwise two complete revoluti.ons plus 18 hol-es that is up to arn B ald aliow the plunger to drop in to the hole in the index plate. (S.2545B Fig.Z) Cut the second tooth.
Rotate the sector arms cl"ockwise so that arm A is again touching the plunger.(tr,ig.r) Uithdraw the pluurger and i-ndex as before. When operatj-ng over the sector arms (e.g.16 divisi-ons, see sheet 5.2545C), the movements of the index crank will agaj-n be in a clockwise direction, though this time the sector arns will be moved aaticlockwise. However, &t the connencement, 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 plus 24 holes, that is just crank rotate the sector arms plunAer.
the index crank clockwise three complete revolutions over arm A. Before the next movement of the index anticlockwise so that arm B is in contact with the
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