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.

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.