How is this chuck mounted?

[Mick BaileyParticipant @mickbailey28509]

Someone nearby has a chuck for sale that has no obvious (to me) means of fitting a backplate as there are no holes drilled. How would this be mounted? It looks similar to the internally threaded light duty chucks for Myfords, but has no thread.

[Robert Atkinson 2Participant @robertatkinson2]

Might never have been mounted on a lathe. Could have been used as a bench vice, on a surface grinder magnetic chuck or held in a larger chuck on a big lathe for a few examples.
I think I can see faint circular marks that could be evidence of stick-on feet. This would support use as a bench vice.

You will need a faceplate…

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

I think I can see faint circular marks…

Given that it is a four jaw chuck, the crop circles you see are the same as nearly every other four jaw chuck: they retain the screws that move the jaws.

[Martin ConnellyParticipant @martinconnelly55370]

It may have been used in a larger 3 jaw chuck to give the 4 jaw utility without having to change a much larger chuck on and off a lathe.

Martin C

[old martParticipant @oldmart]

There is plenty of metal there to drill and/or tap should it need to go on a backplate. Check the thickness in the cavities, there may be enough wall thickness for front mounting. I fitted a very small flange diameter backplate to a 160mm four jaw using 8 small studs just outboard of the register similar to yours avoiding getting too close to the jaw screws. I don’t think the mystery of how the back has no mounts will ever be answered.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mick Bailey, I have a similar or even the same chuck, and a backplate with a short register that fits into the bore of the chuck is fitted into the recess and held by four 3/8″ x 20 TPI cheese head bolts from the front, with the front of the holes counter bored, so the heads are slightly below the chuck face.

As DC31k says, the circles are for pins that retain the jaw screws.

Regards Nick.

[Mick BaileyParticipant @mickbailey28509]

I’m familiar with the mounting method, it’s the absence of such which I wondered about as they’re usually drilled at manufacture.

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