Old Myford lathe: thread size

[anonymousrapscallion]

Hello all.

I got myself an old Myford ML8 wood lathe and as with any old tool, there w as a bit of fettling to do before it was ready for work (well quite a lot, actually). Anyway, I eventually thought I was ready to begin turning, but w hen I pulled the tailstock clamp lever, it snapped off in my hand. On inspe ction, it seems that the previous owner had it screwed into the nearside of the clamp wheel, rather than running through it and screwing in to the far side; the former arrangement is pretty much bound to cause fatigue and ear ly failure, whereas the latter is correct and far more durable.

So, I am left needing to obtain threaded bar, or a blank bar plus a suitabl e die.

As best as I can measure on the stub of the broken handle, the fitting is 5 /16 inch, 28 threads per inch, which makes it a UNS thread. Now here is whe re I am confused: Tracey Tools sell a die at my measured specification (htt ps://

but ebay sellers seem only to be of fering 5/8 UNS 27 tpi. Can there really be a UNS 28tpi thread and a 27tpi?

The fact is that my measuring and extrapolating from a 1/4 inch stub means that I cannot be certain that 28tpi is the correct thread for my component, if 27tpi is a possibility.

A follow on question: if 5/8 UNS does indeed come in both 28tpi and 27tpi,w ould each fit the other satisfactorily over only around 1/4 inch of thread?

Thanks for any advice.

Ant.

[Phil Addison]

Screw threads are fussy, they have to be the right TPI and the correct threadform.

Buy a 28tpi bolt and see if it fits.

Learn about threadforms here

Google for "Myford ML8 spares" and "Fasteners FAQ"

Phil A

[The Other Mike]

Any chance the material has yielded across the thread and giving you a false pitch measurement?

I would expect the thread is actually a 'proper' UK derived thread rather than some bastard American thing.

Take your pick from

5/16" 26 tpi BSB 55 deg / 5/16" 26 tpi BSC 60 deg

[newshound]

I was going to say something like that.

[anonymousrapscallion]

Thanks for the replies.

I don't think that there is any error due to yielding/deformation of the ma terial. The broken stub still fits the threaded hole that it broke in and t here is no way that leverage applied to a 5/16 bar is going to distort both thread end and the hole that accommodates it; the bar will snap before tha t happens, as indeed it did.

I also don't think I could be in error on the thread count to the extent of 4tpi; there are very clearly 7 threads over my measured 1/4 inch, whereas

24tpi would be only 6. Gauging the difference between 27tpi and 28tpi is a different matter and that definitely falls within the range of plausible er ror on my part.

Cheers.

Ant.

[Bob Minchin]

Myford threads are almost all BSF apart from small sizes which are BA I have yet to come across a BSW thread on mine (1979 ML7RB)

[anonymousrapscallion]

Forget my last reply;I mis-read the suggestion of 26tpi as 24tpi. Doesn't inspire confidence that my observation/counting skills are up to much!

Ant.