# 6 Inch-Self Centering Chuck



## Sundossa12 (Aug 18, 2013)

I have a Craftsman 6 Inch, Model Number 101.07301    I would like to find a self centering chuck. Ive seen them on Ebay and different vendors but Im overwhelmed with the selection.  Can anyone recommend a decent chuck that will not break the bank.   Im just starting out and the independent chuck justs take the fun out of it. 

Thanks


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## Terrywerm (Aug 18, 2013)

I am not speaking from my experience here, but based on what others have reported. Shars offers some chucks that others have reported on favorably, decent quality with a reasonable price.


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## wa5cab (Aug 18, 2013)

Sundossa,

For the 6" 101.07301, Sears originally sold two versions of a 4" diameter 3-jaw chuck.  The cheaper one was tightened by a handwheel and pin spanner.  The slightly more expensive one was tightened with a square key driving a gear in the side of the chuck.  I would go for the latter, personally.  You shouldn't put anything larger than a 4" on the machine.

The first thing to check when looking at an assortment of 4" 3-jaw chucks is how they attach to the spindle.  The spindle nose threads on your machine are 1"-8.  So a chuck with anything other than that will not fit and can be ignored.  For example, the Atlas 618 and the later Craftsman version, 101.21400, has 1"-10 spindle nose threads.  Chucks for those machines will not fit yours.  Chucks advertised on eBay as being for Atlas and Craftsman 6" lathes will almost always (unless the seller is clueless) be 1"-10.

You may also see some chucks advertised as "flat back".  These have no spindle mount.  You will have to buy or make a backing plate with 1"-8 female threads and fit it to the chuck.  I wouldn't recommend you try that as a first lathe project, even though a 4" 4-jaw will just chuck a 4" backing plate.

Robert D.


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## shoeboxpaul (Aug 18, 2013)

My 2cents worth. I recently purchased a 3 jaw scrolling chuck and it was a Shars (Made in China). It came with the adapter to fit my spindle but, to my surprise it is NOT a plug and play. The adapter has to be machined. Threads were fine but, the other surfaces had to be sized.  I wrote the seller because the unit was supposed to fit the 6" Atlas lathe. I was informed that by machining the adapter it will run more true on my lathe.  My take is that it is easier and cheaper to stock a generic adapter. Just wanted to pass this along so you are not blind sided when you open the box. Ask before purchasing. This could be one reason for the lower price.


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## kd4gij (Aug 18, 2013)

With a threaded spindle. It is best to finish the back plate mounted on the lathe it is going to be used on. That gives the least amount of runout.


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## Terrywerm (Aug 18, 2013)

shoeboxpaul said:


> My 2cents worth. I recently purchased a 3 jaw scrolling chuck and it was a Shars (Made in China). It came with the adapter to fit my spindle but, to my surprise it is NOT a plug and play. The adapter has to be machined. Threads were fine but, the other surfaces had to be sized.  I wrote the seller because the unit was supposed to fit the 6" Atlas lathe. I was informed that by machining the adapter it will run more true on my lathe.  My take is that it is easier and cheaper to stock a generic adapter. Just wanted to pass this along so you are not blind sided when you open the box. Ask before purchasing. This could be one reason for the lower price.



New backing plates are not plug and play for any lathe, and it is standard practice when purchasing a new chuck and back plate to first mount the back plate, then turn the surfaces that the chuck will mate up to. This ensures that the chuck mounting surfaces run true with the spindle in _*that lathe. *_The chuck is then fitted to the backing plate. As the others have indicated, that is the way you achieve the least runout with that chuck. It is not only desirable to do this, it is darn near an absolute necessity if you want to achieve any accuracy with that new chuck. Now, if you took that chuck (fitted for your lathe) and mounted it on someone else's lathe with the same mount, it will not run anywhere near as true. Every spindle is slightly different, no matter what type of spindle you have, and chucks are not directly interchangeable from one machine to the next just because they have the same thread. Same thing goes if you purchase a used chuck; it is best to purchase a new back plate, then machine the back plate to fit the chuck to it.


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## shoeboxpaul (Aug 19, 2013)

Thanks for the info. I have never been involved with the purchase and mounting of a chuck prior to this one. I would have indicated the mount prior to using even if it was "plug-n-play". I have a 4 jaw scrolling chuck and it does not turn true. Back when I purchased it through a friend that was a German trained machinist and retired from the Glenn L Martin factory, he did something that overlooked the simple. Instead of removing the adapter, he took the front of the chuck off and machined the face of the chuck and added shims between the two halves. He assumed the nice looking adapter was correct.  He never got it right and I still have it. I may never get it right so I purchased the Shars to replace this unit a couple months ago. Have not had the time to mount it. Luckily, my independent 4 jaw chuck has been able to handle my needs to date. I have become quite proficient at centering things with a dial indicator. 
Paul


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## DAN_IN_MN (Aug 19, 2013)

shoeboxpaul said:


> Thanks for the info. I have never been involved with the purchase and mounting of a chuck prior to this one. I would have indicated the mount prior to using even if it was "plug-n-play". I have a 4 jaw scrolling chuck and it does not turn true. Back when I purchased it through a friend that was a *German trained machinist *and retired from the Glenn L Martin factory, he did something that overlooked the simple. Instead of removing the adapter, he took the front of the chuck off and machined the face of the chuck and added shims between the two halves. He assumed the nice looking adapter was correct.  He never got it right and I still have it. I may never get it right so I purchased the Shars to replace this unit a couple months ago. Have not had the time to mount it. Luckily, my independent 4 jaw chuck has been able to handle my needs to date. I have become quite proficient at centering things with a dial indicator.
> Paul



I guess his training was in using the machines not setting up new tooling.  

What about removing the backing plate, machining it true, assemble the chuck without the shims, and put a new surface on the chuck?  What thickness of shims did he use?

Without a heads up, I probably would have thought the backing plate was true too. :whistle: :whiteflag:




I did not know that a 4 jaw self centering chuck existed.  Thanks for the learning opportunity(s)!

I have a 4 jaw independent chuck without a backing plate.  This thread is a great heads up on putting a backing plate on it!


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## Terrywerm (Aug 20, 2013)

Glad you fellas found this useful, as that is what this forum is all about!!

As for 4 jaw chucks, I have never seen a 4 jaw self centering chuck, but have heard mention of them from time to time. It might be that someone was asking if they exist, but I don't remember for sure. I am not saying that they do not exist, only that I've never seen one. Guess I was just never in the right place at the right time! 

Four jaw independent chucks don't need to be set up to run true like 3 or 6 jaw chucks do, or any kind of self centering chuck, as they do not need to run to such close tolerances. When using a 4 jaw independent chuck, if you need a work piece centered, you always have to use a dial indicator to dial in the part. If you are turning something offset, such as an eccentric for a steam engine, the chuck does not need to run true then either, you still have to dial in the offset using a dial indicator. Thus, there is no need for a true running back plate on a 4 jaw chuck. The only thing on a four jaw that needs to run true is the face, it needs to be square to the spindle.

The practice of machining a back plate to run true on a particular lathe is necessary with faceplates also, especially on lathes with threaded spindles. Chucks and faceplates on machines with tapered spindles and cam lock spindles should at the very least be checked also, and will usually require a cleanup pass in order to run true when moved to a different lathe.


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## Codered741 (Aug 20, 2013)

We had a 4jaw self-centering chuck in Grad school.  Never saw much use, save one time we needed to make a bunch (30ish) of 3" square peg, round hole adapters.  At which point it was a life saver.  I couldn't imagine trying to dial all those in individually...

So if you turn a LOT of square stock, it could be worth the investment.  However, other than a once a year class project, and this oddball project, that particular chuck never got used.  

-Cody


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## shoeboxpaul (Aug 20, 2013)

Dan,
I have it on the bench next to my lathe bench, look at it occasionally and shake my head. I haven't had the time to fool with it. First thing to do would be to true up the adapter. Then assemble it, determine how true it runs and then determine what to do.  I am more concerned about getting my 3 jaw chuck mounted and won't have time for that for at least another month. I always remember people talking about how much free time people have when they retire. Maybe they were joking and I was too young to understand.


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## Sundossa12 (Aug 24, 2013)

This has been a great thread. Thanks for all the help. The "1x8" Thread Tip was fantastic, really helped me with my search.   I also like the tips on "Truing" the adapter flange if needed.   Thanks


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