Hello Harry,

One approach is to set up for thread cutting and take just a skim off the flank of the thread on the adaptor with it mounted into the lathe MT socket. A second approach is to run a 12 tpi die along it if you have one, or even a 12 tpi tap [bottoming] held in a tool holder in the tool p[ost to use as a thread chaser. Don't overdo it, you are after all trying to take off only a few thou without altering the thread form.

Regards Brian.

may be worth checking the spigot as well.

regards

Geoff

Hi Harry ,

If the threads really are tight scrap it or send it back for a refund .

Myford spec for spindle nose dimensions including thread is well known and no excuse for not getting it right .

As said register may be the problem but it may only be a very small amount oversize or just oversize relative to your chuck .

Best thing to do is to measure it – should be size to 0.0002 small .

If no suitable micrometer cover whole of register with either HiSpot blue or thin lines of marker pen and tentatively screw chuck on .

Scrape marks will immediately show where the problem lies .

If generally tight polish in lathe very gently – a small bit at a time – with slipstone and oil .

If local high spots stone them away with adaptor static .

Note that the difference between a very tight fit and a precision locating fit is less than 0.0002 inch – so you may only be dealing with very small errors .

Myford genuine used to make their chuck backplate registers as near as practical size for size on lathe spindle register and advised hand scraping the backplate bore if tight – so again some very tight tolerances to work with .

Regards ,

MikeW

Harry,

Haven't noticed anyone stating the obvious – because it is obvious – but can be overlooked. Make sure that both threads are absolutely clean and lightly oiled before fitting together.