Jacobs Chuck Arbour

[peterw3035]

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 ??

 

[Myfordman]

34 is the chuck number. jt6 is the taper in the back. Extraction of the male JT is done with purpose made wedges.

 

[peterw3035]

Hi Bob, I had read about wedges but there is no shoulder on the arbour ??

 

[parvum]

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

 

[Inspector]

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.

Pete

 

[peterw3035]

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.

 

[Phill05]

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.

 

[Tris]

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

 

[peterw3035]

Thanks All, I do have an adaptor but just wanted to try & improve the chuck I have.

 

[Phil Pascoe]

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.