Need help with my lathe chuck size

[stewart leggParticipant @stewartlegg79705]

HI

I have recently got a unimat metal line micro lathe…

I have bought a 12×1 50mm steel chuck from chronos.. part no 145026 and it appears to be too big? I have recently bought a drill chuck 12×1 for it and it fitted fine…have they sent me the wrong sized chuck by accident? many thanks in advance for any advice you can give me..

[stewart leggParticipant @stewartlegg79705]

just a quick bit of advice needed thanks

[Howard LewisParticipant @howardlewis46836]

Delving a long way back into my memory banks, I made a couple of bits for someone with a Unimat. Certainly the mounting thread on the Tailstock was 12 x 1, (Still have the Taps ) and so was that on the mandrel. But it was in the dim and distant past.

So it is very likely that the 50 mm chuck will need a backplate to suit it.

At the risk of teaching granny to suck eggs, Once the backplate has been threaded 12 x 1, with a register to suit the Mandrel, the O D should be turned down to provide a really snug fitting register in the chuck

In this way, you will produce a register on the backplate which is as concentric as possible to the Mandrel, so that the chuck runs as concentric as possible.

If it is a 3 jaw, it will not hold work absolutely concentric. Do not be surprised at a run out of 0.075 mm. Such things do happen. If you need to have two ( or more ) diameters absolutely concentric, they have to be produced without disturbing the work in the chuck while each diameter is turned.

HTH

Howard

[JasonBModerator @jasonb]

As they seem to do the chuck in both M12 and M14 x 1 it is quite possible they have sent the wrong one, if you have a pair of digital callipers measure the inside of the thread and if you get about 13mm then you have the M14 one.

These chucks are ready threaded so what was said above about backplates won't apply

Edited By JasonB on 28/07/2020 19:51:19

[stewart leggParticipant @stewartlegg79705]

Yes I've measured the thread and it does seem they have sent me the 14×1 version in a 12×1 box…

Will ring them in the morning… Thanks for the reply 👍

[EmgeeParticipant @emgee]

Stewart

Mention as well for the SL lathe M12x1, they also list an M12 which may be coarse rate of thread.

Emgee

[stewart leggParticipant @stewartlegg79705]

Ok Emgee

Will also bear that in mind…ive just measured the inner thread of the chuck and it is 12.8mm so around 13mm..so it must be a 14×1 version?

It also came with an arbor and if I measure the outside thread of that its measuring just under 14mm… and is visisbly bigger than my unimat metal line 12×1 outside thread..

[stewart leggParticipant @stewartlegg79705]

Quick update… It was a 14×1 chuck they sent me by accident all sorted now…

[not done it yetParticipant @notdoneityet]

That part number references the chuck you received. Definitely says threade 14 x1mm.

**LINK**

[JasonBModerator @jasonb]

That's interesting when I looked the other day before posting my reply they had 145025 as M14 and 145026 as M12 both without arbor

[stewart leggParticipant @stewartlegg79705]

Just to help with any confusion… It was originally listed as a 12×1 chuck.. And they were sent 14×1 for the whole batch they received so have updated the listing to 14×1…

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