# Is This Chuck Usable?



## Rick_B (Jun 27, 2012)

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


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## randyjaco (Jun 27, 2012)

It should work OK if the previous owner didn't screw things up. The only way to know is to put it on your lathe, chuck something up and put an indicator on it.

Randy


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## Ken_Shea (Jun 27, 2012)

Agreed,
Have sure seen worse in service.
The jaws do look modified, still should hold round stock plenty good enough.
I'd be sure and make the cleaning include a complete disassemble and clean, looking for burs between the chuck body and back plate, anywhere it fastens up to the lathe as well.

Ken


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## Rick_B (Jun 27, 2012)

Thanks guys - is there any documentation on disassembly and assembly of these chucks?

Rick


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## Ken_Shea (Jun 27, 2012)

You won't need any instructions Rick, just take it apart.
Only about 12 maybe 13 parts in that unit including bolts.
Where have I heard that before :LOL:
I see a grease fitting on it but grease is the last thing I would use personally.
I use way oil just a very light smear and not all over.
Keep the numbered jaws in sequence with their numbered position.


Ken


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## ScrapMetal (Jun 27, 2012)

As far as replacement jaws go, you might check with Cushman: http://www.cushmanindustries.com/products.htm  Your chuck may be too old for them to still carry parts but it wouldn't hurt to ask.

-Ron


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## Charley Davidson (Jun 27, 2012)

Rick_B said:


> Thanks guys - is there any documentation on disassembly and assembly of these chucks?
> 
> Rick



Go to Youtube and search Tubal cain Or 3 jaw chuck he has a 2 part video on them


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## Rick_B (Jun 28, 2012)

out of curiousity, I installed the chuck today with mocleaning or repair.  I used a test bar to check run out - .080" - uh oh.

I think I'm going to disassemble and clean it to see if I can improve that

Rick


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## randyjaco (Jun 29, 2012)

Rick,
I'd try several different size rounds in that chuck to see if there is any difference in run out.

Randy


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## jumps4 (Jun 29, 2012)

before you scrap it you might concider making a soft jaw chuck out of it. and making your own replacement soft jaws? just a thought if all else fails. here is a how to by harold hall http://homews.co.uk/page99a.html
steve


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## Tony Wells (Jun 29, 2012)

With those being one-piece jaws, making a set of soft jaws is quite an exercise for even an experienced machinist. I would definitely follow up with Cushman. If they are unable to help, one option is to weld up the damaged area, and remachine them to spec. if you were to use hardface filler, obviously they would be best ground, but it would be serviceable with a low hydrogen filler, or MIG, and machined back true. This assumes, of course, that there is no scroll damage that would adversely affect accuracy at other chucking diameters.


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## Rick_B (Jun 30, 2012)

thanks for the feedback -I haven't had an opportunity to do much with this chuck in the last few days.  Let me ask this - if I decided to replace this chuck is the back plate usable with a different chuck or are they matched to this specific chuck?  What if any "fitting" would be required to use this back plate with a different chuck?

Thanks
Rick


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## swatson144 (Jun 30, 2012)

If the chuck register (step) on that chuck is larger than the new chuck you could give it a try and see how it runs. 
You might want to take the chuck off the back plate and dial indicate the face and radial on the back plate's chuck register, remove it and repeat. If the runout is good and low and repeatable during the removal / replacements then it was fitted to the spindle correctly and not worn/damaged and can be reused if you can skim the face and set the chuck register back to fit the new chuck.

If the register is smaller on the old back plate I suppose you could press on a ring and machine it to final dimensions but that would be getting towards the same effort as fitting a new back plate.

A lot of times chucks and back plates were used simply because they fit with no consideration to if they fit well and ran accurately.

To do accurate one off work on an existing part you need to use the 4 jaw chuck anyway. The 3 jaw is mainly to quickly chuck up a piece of stock to make something out of. In that case it will work well as long as it has good fit to the spindle.

Steve


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## Rick_B (Jun 30, 2012)

ThanksSteve- sounds like i meedto find some timeforaddtional'diagnostics before I get ahead of myself.


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## xalky (Jun 30, 2012)

Check shars tool for an inexpensive 3 jaw with backing plate. I bought a 6" for my SB 9 and it works great. I had to turn down the back shoulder of the backing plate so as to get more threads engaged on the spindle, but other than that I had to dial it in with an indicator and got it within .001 concentric.


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## Rick_B (Jul 1, 2012)

Thanks Xalky - that looks like a good source if and when I get to that point

Rick


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## jumps4 (Jul 1, 2012)

hi rick
by searching old threads on chucks i located what may be your answer this thread is pretty good
http://www.hobby-machinist.com/show...hucks-(17-pictures)/page2?highlight=cnc+lathe
the condition of the chuck he started with is nearly the same as yours
steve


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## swatson144 (Jul 1, 2012)

Guys we don't KNOW that it is a problem with the chuck. It looks suspect but if that was all it took to be guilty I'd be arrested on sight. 1st things first. Find the problem and address it. It could be a refacing and registering of the back plate on his machine fixes the run out and holding small stock just requires a good drill chuck on a straight arbor.

Certainly buying a new chuck and machining a new back plate will fix the problem.

To me this is a hobby and fixing these problems thoroughly, and cheaply is part of it. .0015 shim on one of my jaws makes near perfection. I wouldn't do it in a production environment, there'd be a 4 jaw on the machine. 

Steve (who figures the surest way to fix a problem is to buy a new machine)


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## Rick_B (Jul 1, 2012)

Thanks Steve - that was a very interesting thread - probably beyond my current capabilities but who kows..........
Rick


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## Rick_B (Jul 1, 2012)

Swatson - I agree about umderstanding the problem and attempting a fix.  I am not going to jump into buying a new chuck just yet.  I haven't found the time to get back imto the chuck - maybe tomorrow : 

Rick


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## Rick_B (Jul 2, 2012)

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​


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## swatson144 (Jul 2, 2012)

Rick_B said:


> 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? ​



The OD doesn't mean as much as the OD of the chuck register (step on the back plate) and the face runout. If the threads were (likely) cut by the backing plate errr blanker? maker? ... they'd be pretty close in runout to the OD of the backing plate. 

What I'd be looking at for a three jaw is the facial runout and the run out of the chuck register. Those two determine how true the chuck can run. If the facial is out by a couple thou and the register is out a couple anything chucked into a perfect chuck would look like a monkey waiving a sugar cane.

The fit of the back plate to the spindle is a combination of the spindle register and the abutment face. Fitting a back plate (for me) pretty much means boring the plate and cutting threads, flipping the faceplate/driveplate/backplate and making the nipple end perfectly match the spindle which is tested by my spindle plug. Once it is flipped back flange side out, it is faced and the chuck register cut.

The spindle plug is a prerequisite IMO to fit a back plate. You can fit one without one but making the plug perfect in every measurement and machining the back plate take about as much time as just sliding by. Goofing up the plug costs a chunk of 2.5" round and not a chunk of 100$ cast iron.



The point of the rambling is you can buy a great chuck and screw up the install and still have craptastic tooling.  Mine is .003 out on it's best hole and I'm good with that. I didn't install it, it came with the machine.  If I need better the 8" four jaw goes on.

Steve


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## Rick_B (Jul 3, 2012)

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 jaws causing the problem. The "modification" is inconsistent both within and between the jaws and you can feel it is gripping very poorly.

Rick


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## swatson144 (Jul 3, 2012)

Bummer about that. I was hoping it'd go better. But at least you know the back plate is OK.

Steve


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## xalky (Jul 3, 2012)

Rick Here's the one I got for my SB9. It'll fit yours too. http://www.shars.com/product_categories/search/?search=202-5405  You' cant beat the price for a chuck and backplate with inside and outside jaws. It has served me well so far. I had to dial it in by rotating the chuck on the back plate to the best set of holes and then knocked it around a little with a plastic face hammer and indicated as I went, before I tightened it permanent.  It's within .001 on a chucked piece of 1/2" polished drill rod. Works for me.


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## Rick_B (Jul 5, 2012)

I called one of the suppliers I got from another 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


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