How to evaluate a used chuck.
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  1. #1
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    Default How to evaluate a used chuck.

    There is an old 10" D1-4 four jaw independent that came with my lathe- it got thrown in with the deal. No pins in it. I just found a set of pins from MSC, as I want to try out the chuck.
    No idea on brand, but it does have 7/16" threads so it may be a domestic product. The round inset aluminum badge is worn smooth.

    Although the surface shows some wear and dings, the jaws run smooth, are numbered to the body, and have minimal play. They are also un-scarred. The sides of the jaws are highly polished.

    The taper has some tiny dings/burrs which will be stoned flush.

    Being an independent , it seems like the criteria is a good fit to the taper, so the chuck body runs true, minimal play in the jaws, and most important, the jaws running parallel to the lathe centerline so the part is held on centerline (not bellmouthed).

    Do you all have other tips or tricks to look for when checking out a chuck?

    I am starting to get an accuracy bug....just got a beautiful Fischer live center from a member here!

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    Being a 4jaw, they will work fine even when well used. In fact I have never seen a 4jaw that didn't work fine unless something was broken. I imagine one could be bell-mouthed enough to cause problems but I've never seen one. I have a 12" 4jaw from 1919 that still works fine. The jaws are loose in the slide and the screw but it still holds stock just fine.

    I would grab some pins and slap it on

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    The biggest problem with any used chuck is answering the question:

    "How have the previous jamoke(s) who used this chuck modified, damaged, or otherwise reduced the value of the jaws?"

    I see lots of nice looking chucks that have had one or two of the jaw steps machined away, presumably for a specific operation. The old "We can make this lot of parts much faster if we cut away these steps" idea. Might more than cover the cost of the chuck, but it devalues the chuck from then on.

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    A significant factor for 3 or 4 jaw is the looseness of the jaws. Specifically in what I will call the z direction in and out of the face along the spindle axis. This allows the jaws to rotate out slightly leaving just point contact on your part. Then you are living in chatter city where nothing can save you.

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    I have had a couple problems with my 4 jaw chucks, a couple you mentioned in the original post, but I will outline the importance.

    Chuck #1 is a Bison 8". The problem with this chuck is the PO welded in between all the serrations of the jaws, then reground them (with a toolpost grinder?). I believe the goal was to allow greater clamping pressures on gun barrels without marking the surface. Regardless, this seemed to make the jaws very inconsistent weight. I did not notice this problem until I chucked up a larger piece of work (2"+) and noticed that over 800 RPM, I could feel the vibration in the lathe (a Clausing 5900). I purchased new jaws, but have yet to put a larger piece of work in to see if the vibration is fixed.

    Chuck #2: Old no-name 10" chinese 4-jaw. It was a plain back chuck with a L00 adapter. Only problem is, the adapter (or the chuck) was not drilled concentrically, so again, like the other 4-jaw, at higher speeds, you can really feel the vibration in the lathe. However, realize that the body of the chuck is probably off by .005" or more. I really need to remove the adapter and see where the problem is. I don't use the chuck often, as that lathe has 6 jaw adjust-tru that rarely gets removed.

    You really covered all of this in your original question, just though I would mention as practical examples of why these are important. As for the jaws being bell mouthed, I assume all jaws will get bell mouthed with normal usage. I would expect that good practice would be to grind the jaws periodically (some period longer than other depending on usage).

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    Well I am learning...

    Pulled apart the chuck, and found one of the screws (worm gears) had a bunch of threads broken off on the end, past the retaing cut out.- apparently someone had the chuck jaws greatly extended so they only engaged the last few threads, and then dropped it on concrete or something. Sheared then right off. The jaw thread (pinion?) is in fine shape, go figure. And it works ok, as long as the jaw is not run out very far...

    This looks like American threads, seems to be 5 TPI, square profile. A bit under an inch in diameter. Any idea where one could find a replacement? I could turn one, but the hardening is beyond my ability.

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    I doubt the hardening is that critical....chances are good if you don't harden it, and it begins to wear, it will still not be worn out and dead by the time you are.

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    Quote Originally Posted by GregSY View Post
    I doubt the hardening is that critical....chances are good if you don't harden it, and it begins to wear, it will still not be worn out and dead by the time you are.
    Do you have a material suggestion? Not sure on appropriate steel. I have some 1144 laying around, and some 1018, and some annealed 4130. Or I could buy a piece of whatever.

    The square drive hole is big enough to cut with an end mill so it will not have to be broached.

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    Used to be a guy in Houston back in the late 1970's that made chuck screws by the hundreds for most any size chuck. Some of these screws were close to 2" in diameter and up to 12" long. All he used was 1144 stressproof for them. Also had a drill press set up with a Watts floating chuck to cut the square or hex in the end of the screw. They were not heat treated after wards. I would just use some 4140 heat treated to make them out of without any additional heat treating to the parts afterwards. Ken

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    Quote Originally Posted by stoneaxe View Post
    Do you have a material suggestion? ... I have some 1144 laying around
    I would use this if you have it.

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    Quote Originally Posted by Rob F. View Post
    I would use this if you have it.
    Sounds like a plan. Worst than can happen is it gets worn out, and I won't live that long..!


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