Jacobs Chuck Arbour


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15 Dec 2017
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Romsey, Hampshire
I've recently upgraded and changed lathes from a Draper WTL90 to a Vicmarc VL100, two questions;
1. I have a good Jacobs chuck Nr 34 with a 1MT arbour marked 6JT, rather than buying a new chuck I'd like to separate the arbour and replace it with a 2MT 6JT arbour. Before I go at it with a big hammer, how is it best to separate them?
2. What does the first Nr. eg 34 on the Jacobs chuck refer to ??

Hi Peter, You should be able to knock the taper out of the chuck by using a punch on the end of the taper visible in your picture of the open jaws.
hope this helps, regards Paul
If the above is not the end of the arbour then as a last resort cut it off flush with the end of the chuck. Drill a hole, tap drill size, through the centre of the arbour being careful to stop when the bit goes through. Thread the hole and then wind a bolt in until it bottoms and pops the piece out. You can also instead of threading put grease in the hole and with a snug fitting punch hit the grease and that will hydraulic the piece out.

I've used the thread method to save a very expensive keyless chuck they threw away where I worked because they couldn't figure out how to get the stub out. 🤫

Hi Paul & Pete, I don't think the arbour comes through into the chuck body as the bottom appears solid. Tapping & threading is a good idea but beyond my experience & available tools.
I think a second hand replacement with a 2MT arbour is the answer unless anyone else has any suggestions. I can easily sell this 1MT chuck and probably not be too far out of pocket.
Peter, You could try clamping the tang that's the flat at the thinner end of the shank in a vice and with a bar in one of the key holes try twisting it.
In the same situation I bought an adapter sleeve from Axminster, there's a couple on their eBay shop atm for about £13. Adds about 20mm to the projection but does the job
Open the jaws up, put the chuck in a vice and drill a 3mm hole through the centre of the base of the chuck - the drill will drift near enough to centre as the inside of the chuck is dished. Put the chuck jaws up in a vice so the the arbor isn't clamped, put a nail down through the hole and give it a whack. The arbor will drop out. Two or three minutes and it's done. I did mine to fit 2MT tapers as well.

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