machine 4 jaw chuck to make it front mounting..

[pmurdock]

I bought a 4 jaw Bison Combination chuck (it has a scroll) and thus by default it is meant to connect to the spindle adapter plate from behind. However in the situation i'm facing I will have to mount it to the adapater plate from the front. Bison told me it is totally possible to mount from the front - but the chuck needs to be drilled through in order to accomplish this.

Basically I need to create a new bolt hole circle near the outer radius of the 10" chuck. Has anyone done such a task - and I'm thinking this is going to be a pain because there is an existing 6 holes tapped on the back end. Plus I have to avoid the 4 master jaws as well.

Anyone had any experience doing this - and can perhaps throw out a couple of tips about machining the chuck? Should I do 3 or 4 mounting holes? Bison suggested I use M12 or 1/2"-14 Grade 12.9 bolts.

cheers,
Paul

[chich2]

Do you have a picture of what you are trying to do?

Chich

[Geof]

I have done something similar but not on a Bison.

Do you need to keep the existing threads that are tapped from the back? I drilled similar mountings holes all the way through and counterbored the front side. These holes were already at a large enough radius to clear the scroll.

If some of the six holes overlap the jaw positions just drill additional holes on the same radius between the jaws.

Regarding the suggested bolt size I sometimes think using such large bolts is overkill, particularly when the bolts are right out at the periphery of the chuck. If you are bolting this onto a rotary table or something like that I am fairly sure 8mm bolts would be more than enough and even if it is mounted on a lathe spindle six 8mm bolts would handle all the normal loads.

[BobWarfield]

I drilled through a chuck so I could mount it on a rotary table. It was cast iron and it cut like butter. Very easy work. Just make sure you don't hit the guts of the chuck!

Cheers,

BW

[DareBee]

Why didn't you buy the front mount model?
That is what I use.
http://www.lathe-chucks.com/BISON/BI...OLL-CHUCKS.htm

[pmurdock]

Unfortunately Bison doesn't have a 4 jaw combination chuck in front mount. What is nice about this 4 jaw combination chuck is that you get the benefits of a scroll chuck + 4 independently adjustable jaws. So I can mount an off-center piece and then unscroll and rescroll again (to what accuracy I'm not sure yet).

I'll have some pictures and update the status of this soon. I've decided to go with 4 holes drilled through on the front. I'm going to avoid the original bolt hole circle (in case I ever need to use it in a different lathe that can use the back mount style.

cheers!
Paul

[DareBee]

Maybe mine is a prototype

I also supplied the literature link in my last post.

I believe they are drilled through in the same spot that is tapped on the backmount.

[pmurdock]

the one in your link (4 jaw scroll) doesn't show each jaw as being adjustable? perhaps the image is just wrong? I agree it would have been easier to go with that route if it was possible. are you sure you can adjust each jaw individually on yours? curious..

cheers,
Paul