Myford ML7 Taper-turning Attachment Query

[Nigel Graham 2Participant @nigelgraham2]

The Myford 7-series taper-turning attachment is available from Myford, but pricey so I need be reasonably sure before buying one.

I have explored my ML7 to see where it fits, and how to remove the cross-slide screw (very simply) but my question is about its use.

How do I advance the cut depth?

With that screw and its bearing removed, the compound slide handle has plenty of room but the slide can still rotate only about 50º from “mid-gear”. Removing its T-bolts to set it right angles to the lathe axis puts the mounting slots off the sides of the cross-slide.

So short of making an adaptor-plate, or a special tool-holder with built-in feed-screw*, to let the compound-slide give normal radial feed, am I right I’d need set the slide at 45º and advance the tool by (Depth of Cut X 1.414)**?

Which of course also traverses the tool axially by the DOC value. Not important if the taper is right to the end of the work-piece, or ends on a smaller-diameter section, but difficult for a taper bounded by larger diameters.

So I’d be grateful if anyone knows better, please!

___

 

* Two components screwed to a QCTP holder, if those are not hardened, or a complete lump held by the conventional tool-post stud. For the former, a block on the back end to take a screw that pushes against the back of the tool; and a plate bridging the outer face to hold the tool against the back face of the channel.

The “adaptor plate” alternative: 1/4″ m.s. plate; shallow concentric recess and hole for the top-slide casting and its spigot; tapped holes in its overhangs for the slide securing screws; clearance holes in the plate corners for the cross-slide T-bolts.

.

**By Pythagoras. The diagonal of a square is the side length X the square-root of 2. Useful when making a square along a cylindrical part: further, turning the section to a few “thou” over A/C diameter leaves neatly rounded edges to the square.

[noel shelleyParticipant @noelshelley55608]

For the taper turning attachment No 1429 you need document S2626A the instructions for it. I have it on paper and could get it copied and post to you, though you already have the idea ! Noel.

[Kiwi BlokeParticipant @kiwibloke62605]

30 degrees is a more convernient angle, because sin 30 = 0.5. I can even do the maths in my head…!

And the inconvenient ‘extra’ traverse, resulting from topslide advance, can be compensated for quite easily (similarly simple trig.) if your leadscrew has a handwheel (although I can’t do that maths in my head…).

[DiogenesParticipant @diogenes]

It sounds as if you are asking about cutting a ‘closed’ taper between shoulders?

[Gary YeadonParticipant @garyyeadon51936]

Any pictures available?

[Nigel Graham 2]

On 7 February 2024 at 22:51 Nigel Graham 2 Said:

How do I advance the cut depth?

It is a good question.

There is a block that bolts to the back end of the cross slide. That has a slot in it that secures it to the TT lower part and allows coarse adjustment of cross slide position.

Could you make something that fits into or on top of that slot that would allow fine adjustment? It could look a little like a micrometer adjustable bed stop.

It would be a little difficult to use as you have to reach over the toolpost to adjust, but it would eliminate the longitudinal movement caused by an angled top slide.

With the GHT geared and retracting top slide, that moves the top slide handle upwards. Maybe something similar could be done so the top slide could be set parallel to the cross slide.

If it is mainly the dial of the standard cross slide that prevents it being set parallel, make a smaller dial and squint a bit on the odd occasion you use the TT. A Kipp-style ratcheting handle could then be used.

Edit:

This shows how to overcome the angular limitations of the cross slide:

ML7 Topslide limitations

[Nigel Graham 2Participant @nigelgraham2]

Thankyou!

Strangely, there is ample literature on other turning operations but hardly any details on turning tapers! The more I thought about everyone’s replies the more I realised there is to it:

.

Gary –

The only three photographs I have found are for the taper-turning attachment alone, on the Myford web-site catalogue, in Ian Bradley’s The Amateur’s Workshop, and in a professional training publication.

Mr. Bradley shows a taper-turning attachment in use although not on an ML7. Notably, the compound slide is set at 90º to allow its use, but the heavily-retouched photograph does not show how it is locked to the cross-slide.

His text does not explain how to use the device, but does say:

“.…. One of the advantages [ of the attachment] is that the lathe self-act may be used to traverse the saddle itself. A disadvantage however  [is] with the feed-screw disconnected the cut must be adjusted by slackening the connecting link and tapping the cross-slide forward. In many high-class industrial lathes… the cross-slide is kept operative and puts on the feed without impeding the… taper attachment. “

[Acknowledgements to MAP Technical Publications.]

The chapter describes turning short tapers by the compound-slide directly, longer ones by offset centres (including using the adjustable tailstock-centre, which can be made though Myford also sells a commercial version). However, the text lacks, and I have not found this covered in other books, is how you drive the work to obviate any effect from the combination of drive-dog and non-axial work-piece.

Nor does it worry about the headstock centre not engaging the centre-drilling properly.

T. Nuttall’s National Certificate Workshop Technology – written for professional industrial trainees – is also a bit sparse on taper-turning but shows a retouched photograph of a taper-turning attachment on what the courtesy citation reveals is a Holbrook lathe., on p.178. However the text tells us you need disconnect the feed-screw and nut, and says nothing about adjusting the cut!

The same page also shows a ball-centre, admitting them being rather fragile. A previous post of mine, about peculiar banding appearing on a long taper, elicited advice to use ball-centres when using the offset-centre method.

[Ack: The English Universities Press Ltd., London – date not given.]

 

Some industrial lathes are or were made to generate tapers by gearing both feeds together, but this seems to have been rare. Obviously a CNC lathe achieves the same electrically.

.

Kiwi Bloke –

I take your point but it still moves the tool along the lathe, significant for turning the taper between shoulders. It would worsen the effect on an ML7 because the compound slide can be turned 30º only from the axis, not the cross-travel.

For an actual task I would be tempted to create and print an ‘Excel’ spreadsheet with all the settings calculated: in which case the slide can be turned to its physical angular limit to reduce the off-setting.

My lathe’s leadscrew does have a handle but the cross-slide is still under the control of the taper-turning slide. It may work if the full length of the intended taper is sufficiently less than the limits given by the attachment’s travel (6 inches on the Myford) and its set mounting-points.

.

Diogenes –

Between shoulders: I was indeed considering that.

Another effect of the limited rotation is that the standard arrangement does not allow facing very shallow cones, e.g. to make Vee-pulleys or coned caps with normal tools.

.

DC31k –

Thankyou for the link.

Cut adjustment on the attachment itself would solve the problem although as you say, rather inconveniently.

Worse, potentially dangerous where turning between shoulders, because you cannot feed the tool into the cut without the work rotating. To allow adjusting with the machine stopped, I would groove the work first to depth, and use a narrow knife-tool for the taper itself. Or by the deep end being towards the headstock so the start is in fresh air: still wise to make a run-out groove. Instinct had made me think the opposite so as the saddle advances the tool emerges from the metal.

The top-slide handle is obstructed by the cross-slide handle bearing housing, removed anyway to use a taper-turning attachment. Rather, the problem is that the slide can not be rotated more than about 50º.

 

So following your link…

1) Two columns fitted to the cross-slide to correspond with the compound-slide slots: a neat solution, albeit needing slightly modifying the lathe itself.

2) I see others have long ago made adaptor-plates. If the reduced tool especially if using a QCTP is a disadvantage, use smaller-section tools. Anyway it’s no great inconvenience to use the conventional clamp for these occasional applications. This can be made to cover any angle.

3) Something inspired by the GHT Retracting Tool-slide is a proper version of my idea of fitting a small feed-screw to a QCTP block.

4) Mr. Beecraft’s answer – 2 bars clamped to the sides of the cross-slide – is the simplest! Further tapped holes in the bars may increase the available angular range. The studs should not overload the slot flanges, and that load should be distributed along the slots.  A refinement: full-length Tee-bars with tapped axial holes to carry the side-bars, then some tapped holes along their lengths to make them also long-length Tee-nuts. Make the studs / T-bars slightly short so the clamping is against the slide flanks.

 

Solutions 2) – 4) of course do not need drilling holes in the lathe itself!

1), 2), and 4) would allow shallow-angle cone facing, used in conjunction with a lead-screw hand-wheel and removing the cross-slide screw.

A combination-gearing attachment to generate tapers and cones of any angle limited only by the change-wheels available, may be an interesting challenge….  I’ve enough to do as it is!

——-

I have also examined my Harrison L5 to see if that would accept a taper-turning attachment I’d have to design for a lathe not made to take one! The cross-slide screw is not removable so the nut would have to be extracted – technically simple but physically awkward. However the compound slide may be set to any angle, with the cross-slide hand-wheel easily removed.

 

[Nigel Graham 2]

On Nigel Graham 2 Said:

I have also examined my Harrison L5 to see if that would accept a taper-turning attachment

It is important to realise that the limitations of the Myford one are somewhat caused by the cross slide design insofaras the nut is fixed and the screw moves in and out.

On more industrial lathes like the Harrison, the screw is fixed and the nut moves in and out.

It is worth locating the Colchester Bantam/Chipmaster manual to see how they did their taper turning attachment. It uses a splined leadscrew that can slide in and out of the fixed handwheel (the far end is fixed to the TT), so when using the TT attachment, you can add cut in the normal manner using the cross slide handwheel.

There is an exploded diagram of the Harrison TT attachment in the L5 manual. It might work in the same manner as the Colchester one.

Edit:

For turning offset between centres, I understand there is something called a ‘compensating drive dog’. I have seen it discussed more in connection with a dividing head than with a lathe, but I guess it is the same principle. I wonder if a bell centre drill, with its additional chamfer, would assist in the process.

[old martParticipant @oldmart]

If you are going to turn a taper, take care to get the tool height exactly on the centreline, for both internal and external.

[Nigel Graham 2Participant @nigelgraham2]

Thankyou…

Dc31k –

Sorry, I’m not clear what you mean regarding the Harrison lathe.

The L5 I have has its cross-slide screw location fixed axially in the saddle, as it carries its self-act gear, and the nut is held in a socket in the slide casting by a single countersunk screw from above.

The manual I have (a lathes.co photocopy) does not show anything useful about a taper-turning attachment but has some very brief notes about that fitted to the Kerry lathes. It does say the screw and nut are not affected by its use. My lathe has nowhere to fit a taper attachment, so yours must be a later version.

So if it is possible to fit a taper attachment to mine, it would still need the slide nut removing. This by winding the slide in until screw leaves the nut. Pushing the slide back a bit more then allows rather awkwardly reaching the nut for its removal.

.

One might make a ball-centre without a ball-turning attachment by cross-drilling an annealed bearing ball to fit a centre ending in a pin. It would use a generous centre-drilling so the line of contact is on the wall, not rim, of the hole.

A compensating drive-dog at its simplest is presumably one that can rock against its driving-pin, a bit like one of the pins in a Hooke’s Joint. Possibly, a better form than a conventional dog would be something resembling (or is even) a large die-holder with one handle removed, and the remaining one working through a slot in an angle bolted to the faceplate or catch-plate.

I can’t quite work out just how it would actually move relatively to the catch-plate as the work rotates, but presumably it oscillates slightly radially while also rocking in a plane along the lathe axis.

The same arrangement of course for parallel turning.

If this offset-centre method is so subtle, I wonder why none of the reference books seem to cover it in more than the most basic way!

..

Old Mart –

Oh yes – I know the trap there! Though I think there was quite a bit of discussion on this a while ago on this site, with people quoting experiments that reveal the barrelling effect of a miss-set tool is actually very small, critical only on parts that have to mate accurately.

I would think if you use an adjustable tailstock centre you need ensure its slide is truly horizontal w.r.t. the lathe to avoid it giving the same problem.

 

[Nigel Graham 2Participant @nigelgraham2]

Tra-la!!

Or rather,

Many Thanks to Dennis Rushton for e-posting me information on the Myford lathe taper-turning attachment.

Print in hand, or rather in a polythene bag to keep it clean, I explored the lathe further.

I was surprised to find the device is a bit simpler to use than I’d thought: I had worried too much about having to apply the cut with the compound slide at an angle.

The instructions tell you to set the slide round at 60º, the maximum available.

To be accurate about it, you need use a protractor because this is well past the engraved scale, though once established, adding a second fiduciary mark corresponding to the scale’s 30º point with the slide parallel (0º) will give you the aiming-point for future use.

At that 60º, the radial correction is only 0.003″ per 0.020″ of slide travel; although that can be significant when making matching male and female tapers.

Mr. Pythagoras tells me this gives the longitudinal component as 0.011″ – unlikely to be a problem in most cases.

 

[Author]

Posts