Lathe cross-sli olders.BY “ Duplex

When undertaking heavy turn-

that greater rigidity is obtained bydispensing with the lathe topslideand mounting a specially-made tool-post directly on the cross-slide.

With this arrangement, too, millingoperations on batches of small parts

danger of straining or distorting theing, some machinists consider T-slot into which the central clamp-

ing-bolt fits.After the hole for the clamping-

bolt has been drilled, the work isagain mounted in the four-jaw chuckfor machining the recess for the1/2in. washer. On the other hand,

time might be saved by starting thisdrill hole and also forming therecess when the work was set up forfacing in the iathe. The hole in thebase tapped 3/8 in. B.S.F. takes thesmall, slotted pressure screw (B),and the two remaining 1/4 in. B.S.F.holes are for the attachment of thefence or guide bar (C) used in repe-tition milling operations. The clamp-bolt (D) will be strongest if turnedfrom the solid ; this will enable therather heavy thread to be screwcutand afterwards finished to size withthe aid of a die. The bolt can, how-ever, be built up with an extendedfoot-piece screwed in place, and thejoint afterwards either brazed, orthe end of the bolt can be rivetedover into a shallow countersink.The clamp-bolt should be madefully long, to enable a tool with adeep shank or large material to beclamped in place.

The rectangular washer (E) ismade curved on its lower surfacein the fore and aft direction, in orderto transmit the clamping pressure

Fig. 1. The cross-slide toolholder. andwork fence

are a t t imes more convenient lycarried out.

The toolpost illustrated in Fig. 1was originally made for mountingon the top-slide of a large lathe, butnow, after small alterations, it isused on the cross-slide of a Drum-mond 3-1/2in lathe

The base (A) was made from amild-steel offcut and, after beingfaced on all sides in the lathe, itmeasures 3 in. square by 1-3/4 in. inheight.

The undercutting of one verticalface, as appears in the photograph,should be omi t ted , as th i s wasoriginally provided for accommo-dating large lathe tools when thefixture was mounted on the top-slide.

The under surface of the baseshould be scraped to form a flatbolting surface, so that there is no

Fig. 2. The attachment parts : “ A “--the base ; “ B “-the pressure-screw ;” C”-the work fence

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Fig. 3.“ D “-the clamp-bolt ; ” E “-the saddle washer ; ” F “-the clampplate ; ” G “-the clamp platc pressure-screw

evenly to the main clamp-plate (F)when tilted.

The Norman toolholder, fitted asstandard to the 3-1/2in. Drummond-Myford lathe, is machined with aslot to take 9/16 in. round or squarematerial. This form of toolholder,therefore, provides a convenientmeans of mount ing a machinespindle, for example, when cuttingan axial keyway. When the tool-holder is mounted at the lowest pointon the pillar of the top-slide, theupper surface of a 1/2 in. dia. shaftlies almost exactly at lathe centreheight, and a circular milling cutteror a fly-cutter cannot be used tomachine the upper surface of thework. In order to mount the tool-holder rigidly and at a lower levelon the cross-slide, the attachmentillustrated in Fig. 4 was made up.

The two silver-steel pins fitted tothe plate (F) engage in the slottedholes in the washer (E) and keep itfrom turning.

The square-headed screw (G)engages in the slot in the head of thescrew (B) and raises the clamp-plateto the height required ; these screwsalso maintain the clamp-plate inposition. With this arrangement,the clamp-plate does-not turn, butthe toolpost as a whole is, if neces-sary, rotated after slackening thelower lock-nut.

As wiI1 be seen in the illustrations,the guide strip or fence (C)is attachedto the base by means of two 1/4 in.B.S.F. studs ; the spacing-nuts andlock-nuts then allow the fence to beset outwards in order to accom-modate wide material. A th i rdhole is drilled in the fence to providea fixing for an end-stop to locate thework, or an extension bar carryingthe stop can be bolted to the fence.

With this arrangement, a numberof parts can, in turn, be machinedto a uniform length, and with theirends squared, by, mounting a millingcutter on the lathe mandrel and thentraversing the work across the cutterby means of the cross-slide. Fig. 4. Attachment for mounting the Norman toolholder on the cross-slide

r<_;_-jYODKL ENOINEEIQ

After the first part has been re-duced to the required length,. thesaddle is locked and the remainingparts are similarly machined.

In the same way, material can becut up into equal lengths with acircular metal saw, mounted on anarbor between the lathe centres.

When using the toolpost in thisway, the base of the attachmentshould be kept firmly secured to thecross-slide by tightening the lowerlock-nut fitted to the central clamp-bolt, and the work is clamped andreleased by turning either the clamp-p la te nu t o r the square-headedpressure screw.

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i3”

IFig. 5. The baseplate and pillar of the attachment

When the toolholder is set in thelowest position, a 1 in. dia. cutter canbe used for machining a 1/2 in diashaft.

This attachment consists of a base-plate and a pillar firmly secured inplace. After being filed true orfaced in the lathe, the under surfaceof the base should, if necessary,be cor rec ted by hand scraping .However, scraping should not berequired as, to obtain mating of twoturned surfaces, lathe cross-slidesare usually set to machine the workvery slightly hollow ; i n tool-room lathes this may amount tosome half-a-thousandth of an inchon a work-piece 12 in. in diameter.

The bolt holes should be carefullymarked-out to lie exactly on thecentre-lines of the cross-slide T-slots.The central hole and the recess onthe under surface can be machinedwhen the base is set up on the face-plate or in the four-_iaw chuck forfacing. For mounting the baseplateon the faceplate, the four cornerholes are, in the first instance, drilledand tapped to enable the work tobe held by screws inserted frombehind. The 1-1/4 in. dia. mild-steelpillar is turned to a close sliding fit inthe toolholder. If the fit is too free,the toolholder will slide out ofpos i t ion when i t s c lamp-nut i sslackened and, at the same time,extra tightening of the clamp-boltwill be required to spring the tool-holder and secure it firmly to thepillar. To ensure that the pillar bedsevenly on the base, it is advisable torecess the under surface of the foot,as shown in the working drawing.

A standard 3/8in. B.S.F. bolt willserve for attaching the pillar if thelength of the head is reduced.

The four T-bolls for securing thebase of the attachment to the cross-

slide are best turned from the solid,and either5/8 in. square mild-steelor 7/8 in. round bar can be used.

Round material has the advantagethat it can be gripped in the self-centring chuck for machining thebol t shanks and th read ing the i rends from the tailstock. Finally,as shown in Fig. 6, two flats arefiled on the head to allow the boltto slide freely in the cross-slide T-slots.

As material up to 9/16 in. dia.can be mounted in the toolholder,the attachment affords a convenientway of doing work like milling akeyway in a machine shaft. Theshaft should be saved from damageby using strips of sheet copper toprotect the clamping surfaces.

If more than one passage of the

Fig. 6. T-bolt for securing the attach-ment to the cross-slide

circular mill or fly-cutter is neededto machine the keyway to the fulldepth, the work can be adjusted forthe second cut by unclamping thetoolholder and then raising it on thepillar for the required distance ;but care must be taken to ensure thatthe original alignment of the shaft,at right-angles to the lathe axis,is preserved.

When the work has to be set tooverhang the toolholder for morethan a short distance, and so isliable to spring away from the tool,the end of the shaft should be sup-ported on a packing block or bymeans of a small screw-jack.

A SCRIBING GAUGEBy W. F. Yates

THE drawing illustrates a scribing being so many uses to which the toolgauge, which I have had in use can be put. I would like to state

for some years, and is self- that drilling a piece of 1/4in dia.explanatory, and I would like to brass rod and driving in a gramo-say that the original gramophone phone needle produces one of theneedle has been in use for at least nicest to handle, permanent scribers.six years and is still functioning, Both gadgets are well worth the littlealthough used almost daily, there time required for their making.

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