Opinions/Guidance on Three Jaw Chucks

[jbacc]

Good Morning,

I know the subject has been beat to death and I have searched and read as much as I can on the subject. I have a 6" 3-jaw Bison Set-Tru chuck that has seen better days. After dialing it in on a specific diameter part, it will not repeat on the same part and is off by several thousandths or more. I have taken it apart, cleaned it well, stoned the surfaces and carefully reassembled but the results are the same.

I do notice that I get better results 2-3 thousandths repeatability if I tighten down on the part using only one of the pinions and not the master pinion. In fact, the master opinion gives me the worst results. So, my limited knowledge leads me to believe that there is significant wear in several key components of the chuck.

I began pricing new 6" 3-jaw (adjustable/set-tru) chucks and I can't say I'm surprised but I am experiencing sticker shock, especially when looking at the brands with good reputations like Bison, Buck, Samchully etc.. And, the prices don't include a back plate which is another very high priced item.

I considered used chucks but they are ridiculously priced and I am worried about buying a chuck that isn't any better than what I have already.

I come here to tap into the collective wisdom of the forum members for any suggestions comments, suggestions advise etc. I am a garage hack who enjoys fine tools and this will be used on my recently acquired square dial Monarch 10EE.

Thanks in advance to all.

Joe

 

[DouglasJRizzo]

Opinions are like belly buttons. Everybody has one...

Like used cars, used machinery/tools have a lot of clunkers you have to wade thru to get to the really mint jewels that are hidden.
Obviously, buying new negates that journey.
To me, it boils down to time.
Working at your leisure in a hobby? Take your time and pick thru the used stuff until you find that jewel.
In a hurry to finish a job and get stuff done? Buy new and put it to work.

 

[Mtndew]

It sounds like it's all worn out.
As for the backing plate, just make one. I don't think I've ever bought one when we can whip one up in no time.
You could buy 2-3 used of the same one and piece them together to make one decent one.
Try calling or emailing them, maybe they have reconditioned models for cheaper than new.
Having a good, repeatable chuck may be expensive, but if you're constantly messing with it to get it to run true then you have to ask yourself if your time is worth it.

 

[eKretz]

Either tear it apart and do the work to restore it or bite the bullet and buy a new one. Buying a used chuck only makes sense if it's a Set-Tru - and you are okay with the possibility that you might need to do a little work to it. There is no easy and reliable way to get an uninformed seller to check a scroll chuck out thoroughly.

 

[Peroni]

Bison does sell spare parts. If the jaw slots aren't worn out perhaps a new scroll and pinions can restore its accuracy. There are also places that rebuild chucks. In both cases check the cost, it may be cheaper to just buy a new chuck. There are some good deals on quality name brand chucks if you look hard enough. I just got a new in box 6" set-tru 3 jaw SCA for $900.

 

[akjeff]

Buy a new 6" Bison, and re-use the back plate you already have?

 

[guythatbrews]

Sounds like jaws may be in horrible shape. Maybe you can work on the a little and get better results. Take the thing apart and clean the scroll. It may be full of ancient crap.

 

[eKretz]

Bison does sell spare parts. If the jaw slots aren't worn out perhaps a new scroll and pinions can restore its accuracy. There are also places that rebuild chucks. In both cases check the cost, it may be cheaper to just buy a new chuck. There are some good deals on quality name brand chucks if you look hard enough. I just got a new in box 6" set-tru 3 jaw SCA for $900.

Be careful with this. On old and well worn chucks, the chuck body itself usually takes a pretty good beating on internal round fits and faces. Replacing the scroll and related parts probably will not eliminate non-repeatability issues, though it may improve them. Definitely want to check the jaw slots for heavy wear. If they're heavily worn in one area, even if you grind the jaws true and cylindrical in one spot, changing to another diameter will change the geometrical alignment of the jaw gripping surface and the face of the chuck and your bite will no longer be cylindrical...

 

[jbacc]

Thank you all who have taken the time to share your thoughts and advice. I can't say I disagree with any of it and it seems a new chuck is the best course of action for me, unfortunately. I would love to attempt a repair of my current chuck, but I believe the issue is wear on the internal surfaces above and beyond the scroll and I don't have the skill to deal with that.

The current chuck is forged steel and I am hoping to replace it with another forged steel chuck to deal with some of the higher speeds the Monarch is capable of within reason. I also believe from what I have read the forged steel chucks resist wear better than the cast iron ones?

I will keep my eyes open for a deal but prices for new forged steel set-tru chucks is insane. I do see an integrated D1-3 Bison semi-steel chuck for about 650.00 plus tax but it is not an adjust-tru and without a separate backing plate, I wouldn't be able to make any fine adjustments in the future to account for wear, unless I am missing something cast iron construction not withstanding.

Thanks again, please feel free to add to the discussion including correcting any of my opinions. This is all an education for me and I appreciate it.

Joe

 

[Peroni]

Before finding my SCA I was looking at this Pratt Burnerd. You may be able to mount it to your current back plate and have a beautiful new set tru chuck for under a grand. Not that Bison are bad chucks but I rank PB as being a little better in my experience.
Pratt Burnerd 3 jaw set tru chuck

 

[jbacc]

Before finding my SCA I was looking at this Pratt Burnerd. You may be able to mount it to your current back plate and have a beautiful new set tru chuck for under a grand. Not that Bison are bad chucks but I rank PB as being a little better in my experience.
Pratt Burnerd 3 jaw set tru chuck

Thanks, I have heard the Pratt Bernerd Chucks (PBA) are made in China and not the same quality they once were.

 

[Peroni]

Thanks, I have heard the Pratt Bernerd Chucks (PBA) are made in China and not the same quality they once were.

Current ones I believe are made in Slovakia (?) and marked Pratt Burnerd America. I have one and it's very nice and quite accurate. I think the one I linked to was made before that era as it is still marked Pratt Burnerd International.

 

[dkmc]

Mark and use that one pinion that's giving the best results.
Also tighten lightly then 'tap it around' to get things to settle, might get it better.
It also might help if you mentally command the workpiece to do your bidding while making the above adjustments

 

[jbacc]

Current ones I believe are made in Slovakia (?) and marked Pratt Burnerd America. I have one and it's very nice and quite accurate. I think the one I linked to was made before that era as it is still marked Pratt Burnerd International.

Thanks again, I just sent the seller a message asking where it was made and what it is made of. I found a Bison forged steel chuck with integrated D1-3 mount but it's not an adjust-tru...Oy.

Bison 6" Scroll Chuck Steel Body D1-3 Mount 3 Jaw 7-823-0633 | eBay

Find many great new & used options and get the best deals for Bison 6" Scroll Chuck Steel Body D1-3 Mount 3 Jaw 7-823-0633 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[Mtndew]

I also believe from what I have read the forged steel chucks resist wear better than the cast iron ones?

You definitely want a steel chuck.
I don't think I've ever seen a cast iron chuck. It would be way to brittle for the clamping forces needed.

 

[jbacc]

You definitely want a steel chuck.
I don't think I've ever seen a cast iron chuck. It would be way to brittle for the clamping forces needed.

Semi-Steel is the name used for cast iron chucks and there are probably more of them offered than forged steel. Thye are cheaper than forged steel chucks and generally have a lower rated maximum rpm rating, at least that is my understanding.

 

[dkmc]

You definitely want a steel chuck.
I don't think I've ever seen a cast iron chuck. It would be way to brittle for the clamping forces needed.

"Semi steel" chucks have been around for 100 years. Common in 4 jaws.

Edit jbacc is the quick draw typist this afternoon!

 

[L Vanice]

Before finding my SCA I was looking at this Pratt Burnerd. You may be able to mount it to your current back plate and have a beautiful new set tru chuck for under a grand. Not that Bison are bad chucks but I rank PB as being a little better in my experience.
Pratt Burnerd 3 jaw set tru chuck

That is a Pratt Burnerd Setrite (adjustable) 6" chuck, which is only made with a steel body. Note the six 1/4-20 mounting screws that fit tapped holes in the adapter. Buck Ajust-Tru 6" chucks have the same six screws and either brand of chuck will fit on either brand of adapter. The Chinese BTC chucks are copies of the Buck and also fit those adapters. Bison adapters do not fit chucks with six screws.

Larry

 

[jbacc]

That is a Pratt Burnerd Setrite (adjustable) 6" chuck, which is only made with a steel body. Note the six 1/4-20 mounting screws that fit tapped holes in the adapter. Buck Ajust-Tru 6" chucks have the same six screws and either brand of chuck will fit on either brand of adapter. The Chinese BTC chucks are copies of the Buck and also fit those adapters. Bison adapters do not fit chucks with six screws.

Larry

Thank you, Larry, very helpful information.

Regards,

Joe

 

[jbacc]

"Semi steel" chucks have been around for 100 years. Common in 4 jaws.

Edit jbacc is the quick draw typist this afternoon!

LOL, thank you...