Chuck Advice

I'm contemplating getting a smaller chuck for my 4" rotary table and I am leaning towards a 80mm chuck of the type that use's tommy bars in place of a chuck key. I've not used this type of chuck before so I wondering what are the pro's & con's ? I don't do a lot of work with the rotary table and I am drawn to this type of chuck not because it's cheaper but for it's lower profile, would welcome comments please.

Cheers H

Harry I presume you mean a three jaw I personally would find a four jaw more versatile

Roy

I have a small 3-jaw scroll chuck on my EW and I use a tommy bar on that. Most of the time it works very well just by hand-holding the body and I don't need to tighten it so much. When I do need more grip, I also use a rubber strap device (can't remember the trade name) to grip the chuck body whilst I tighten (or untighten) the scroll with the bar.

On balance, I probably cannot grip things as tightly as with a 'keyed' chuck, but it is a low profile chuck and much better than the 3-jaw that came with the lathe. This was far too big and stuck out too far, causing chatter on some work. Getting the work nearer the EW's front bearing really helped with this.

I'm not sure what you are using the rotary table on but if its on a mill (and yours is limited on vertical height) the depth of the scroll chuck might be more important to you than it's grip.

Regards,

IanT

of the type that use's tommy bars

I wouldn't recommend them for milling etc on a rotary table, the chuck key type have a far better grip

Not a good type for arthritic/painful fingers either, especially if you are doing a lot of chucking

The third disadvantage is that you always need 2 hands to tighten/release a tommy bar chuck so you can't hold the workpiece

Edited By Ady1 on 04/03/2014 12:09:37

Hi Harry

It's true that you cannot readily get the same grip with a lever chuck as a geared scroll chuck but used with common sense they're perfectly fit for purpose and have often been provided with small lathes.

One caveat is that it will need a fitted backplate for your application as the rear ring of the chuck has to rotate as the chuck is tightened thus cannot be directly clamped down on to the table. Ideally the backplate should also have a tommy bar hole as otherwise the stress of tightening my be taken by the worm gear of the table if the table clamp arrangement is not very efficient. I have a 4" Sharp rotary table on which the only clamping is by means of a small grub screw. With use of two tommy bars, no problem.

Given the backplate requirement you may lose some of the height advantage compared with a front fixing geared scroll chuck which could possibly be bolted directly to your table, subject to the tee slot arrangement of the table being suitable. The lever chucks are quick to use, the locking ring being readily rotated by the fingers and then nipped up with the tommy bars. I'm not sure if an 80mm version is readily available though TOS do a nice one of 65mm. If you really want to push the boat out however MSC do a super 6 jaw 80mm Bison but do check the price before you order!!!

Edited By michael m on 04/03/2014 12:07:19