Tight thread

[Harry WilkesParticipant @harrywilkes58467]

Need some advice please I recently purchased a Myford chuck adaptor to mount a chuck onto a rotary table, the chuck in question screws onto my S7 without any problem however when I screw the adaptor into the chuck it goes tight so whats the best way to ease the thread on the adaptor ? Any advice welcomed .

[Harry WilkesParticipant @harrywilkes58467]

[Brian WoodParticipant @brianwood45127]

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.

[Michael GilliganParticipant @michaelgilligan61133]

Harry,

At the risk of "playing the same old record"

Before you start easing threads … Are you absolutely certain that it's not the plain register that's wrong ??

There are previous discussions on this forum.

MichaelG.

.

Edit:  Read through some of these.

Edited By Michael Gilligan on 10/01/2014 10:02:36

[Geoff RogersParticipant @geoffrogers81118]

may be worth checking the spigot as well.

regards

Geoff

[DMBParticipant @dmb]

The mandrel thread has been used any number of times has slight wear. The adapter is new and thread has no wear at all. That is, I think, the likeliest explanation for apparent tight thread. Could also use a hand held thread chaser, which might not be so brutal as any other, rigidly fixed device. I used on to clean off swarf jammed tightly on the mandrel thread. If it dont go, dont force it!

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

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 WilkesParticipant @harrywilkes58467]

Thanks for all suggestions and comments it looks as if it's getting tight just before the register but over the weekend I intent a much closer look at the problem,

Again thanks H

[RobboParticipant @robbo]

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.

[Harry WilkesParticipant @harrywilkes58467]

Guy's found the problem after making sure the threads were clean and taking up Robbo's suggestion of a little light oil I was able to screw the chuck on further but still very tight when it start over the register and it was at this point that I thought try one of the other chucks I have (Doh why didn't I think of it before) this one screwed on as it should so I need to do a little scrapping and it should be OK.

Cheers H

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