Thread: Is This Chuck Usable?

The chuck that came with my Heavy 9 is a 6" 3 jaw scroll chuck. It has a back plate attached thread 2-1/4 - 8 which fits my spindle. My concern is that it appears the shape of jaws has been reconfigured





Can this chuck be used as is (after saome clean up of course)? I think the lower limit of stock size would be a cocern but what about bigger size stock? Are replacement jaws generally available? My concern is that the grip of the chuck and centering may be compromised.

Thanks!
Rick

The chuck should be fine. You can replace the jaws that is a common brand of chuck but it would probably be cheaper to just buy a new one, maybe not a cushman but something else.

yes, someone ran a die grinder in the jaws as it was turning who known why..?? maybe for a special job.

Thanks guys - just out of curiosity I installed the chuck prior to any disassembly or cleaning. I used a test bar to check run out - .080" - Yikes.

I think I'm going to take it apart and clean it up to see if I can improve that.

I heard and read about 2 piece jaws - are these a set of jaws where the top portion can be removed and reversed (or another set of jaws installed) while the lower half remains in the scroll mechanism ?

Thanks
Rick

.080 is a lot .
Check that the jaws are installed in order .
You have it right about two piece jaws .

Am I wrong to think a clever person with well-equipped shop has the ability to rescue those jaws?

Of course, make sure they are properly installed, and if they aren't numbered, number them, once you put them in the optimum location.

I haven't much opportunity to work on this chuck in the last few days. If I decided to replace the chuck would the back plate be useable with a different chuck or are the back plate and chuck "matched"? What, if any, fitting would be required to use the existing back plate with a different chuck?

Thanks
Rick

From the stickies above .
Useful even if you don't replace the chuck .
Link : Machining A Chuck Adapter

Yes it's useful.

1) purchase boat

2) purchase rope

3) tie rope to boat and chuck

4) toss chuck overboard.

Instant anchor!

Omit (1) above if you already have a boat.

Backing plates are matched to the chuck. But they can rematched by cutting a new register surface to a different chuck. Although sometimes a chuck can be if dialed in to a backing plate without machining. I've fabricated backing plates and they came out okay. The trick is to cut the spindle threads first then machine the face and register while threaded onto the spindle. Then drill and tap the mounting bolt holes with the chuck mounted to the register.

OK - I started looking at this chuck this morning and tried to disassemble the backing plate. I removed the 3 bolts from the front side of the chuck,and was expecting the backing pate to simply come off the chuck - no go. It seems that it is stuck.''i squirted some kroil on it but am wondering if there is something else holding the chuck to plate? Is there some kind of nose that fits into the chuck (press or slip fit)? The pictures I have seen so far looks like the backing plate is a flat surface where it meets the chuck and the only attachment points are the bolts.

Thanks
Rick

Well I got the chuck apart with only minimal abuse. I put the back plate bolts back in but did not tighten them and then tapped them lightly and the plate popped off. Did the same thing with the chuck halves. Lots of dirt, grime and chips inside the assembly. I cleaned up the back plate and reinstalled it and had about .002"run out on the outside diameter of the plate. I thought that was pretty good. I'm wondering though if that really means anything? I'm going to clean up all the chuck parts and put it back together and see what I get.

BTW - the jaws and chuck are both clearly marked for position (1, 2 and 3) and all jaws were correctly located.

Rick

I got the chuck cleaned up from all the dirt, grease and grime. I checked run out on the back plate registration surfaces - less than .001". After re-assembly I checked the outside of the chuck circumference and got less than .005" on a rough surface. With a bar chucked up I was back to >.090". I believe it is the maws causing the problem. The "modification" is I could sis tent both within and between the jaws and you can feel it is gripping very poorly.

Rick

I got the chuck cleaned up from all the dirt, grease and grime. I checked run out on the back plate registration surfaces - less than .001". After re-assembly I checked the outside of the chuck circumference and got less than .005" on a rough surface. With a bar chucked up I was back to >.090". I believe it is the maws causing the problem. The "modification" is I inconnsistent both within and between the jaws and you can feel it is gripping very poorly.

Rick

For once, I gotta disagree with Jim Rozen. I would not own a boat if it was given to me. Chucks like that make great door stops! It might make a sorta OK vise for holding round stock, as long as you didn't need to grip the inside... note this chuck would have been supplied with two sets of jaws, inside and outside jaws. You only have one of those sets, and they seem to be FUBAR.

I'm curious to know where one might get new jaws for a chuck like that, I spent some time on the Cushman website and don't see anything like replacement jaws for older chucks.

So back up a bit... clamp a relatively round part by expanding the jaws. If that shows round the problem lies with the hand cut points at the center tips. To keep it as a beater chuck, weld the points back up to standard height and have them re-milled at 60 degrees to regain a point of contact thats close to being on center.
At worst if that doesnt work, keep the back as a mounting plate for a new chuck. I had to do this for an old 1903 Dalton that had a bastard spindle thread that was something like 1-1/8 x 9 tpi. That 4 jaw was sprung and would need to be completely realigned with EXTREMELY POOR repeatability for even the smallest of moves. The jaws were sprung as well as the jaw screw trunnions. Bought a new chinaman 3 jaw chuck for $75 and all was good. The 4 jaw backing plate was a tad light so I ended up using another face plate I had which required drilling the chucks' back. ws

Rude - i've got a question into Cushman to see if they are available. I'll update when/if I get an answer.

Rick

Edit -oops forgot to mention I have a boat too :-)

I called one of the suppliers I got fromanother forum - they were extremely helpful - they took the chuck and jaw information and called me back in a few hours. Based on their research the chuck is likely an early 1960's vintage and no longer supported by Cushman so jaws will be very scarce. They also gave me pricing on two direct mount chucks with 2 piece jaw sets - a new import for $175 and a used bison tru-adjust for $275 - they also said that if they had or could get jaws they would cost more than either of the chucks they had.

A fellow member on another forum is letting me borrow a chuck to get started so I have some time to decide if I want to go with a replacement chuck or try to repair the jaws.

Rick

get the new chuck, you wont be sorry.
besides, an old 3 jaws makes a great vise for holding round stock for rough work on the bench so you'll get another tool out of it.

Why not try grinding the jaws?