Need a little chuck advice........
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  1. #1
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    Question Need a little chuck advice........

    Due to the events of life, I haven't been on here in quite awhile......but it's the only place I know of where experience is the rule.

    I have a 1920 Hendey lathe that I rebuilt some years back and it's served me very well. It has a 10" Chinese 3 jaw mounted, which has always been very accurate. Or at least it was. The chuck started exhibiting signs that it needed to be cleaned so I disassembled it, cleaned everything and reassembled it. Note that Quan Lee (or whoever) mis stamped the jaw numbers, but it was assembled so that all three jaws meet on center. (I doubt if the cleaning had anything to do with the following).

    I put a piece of stock in the chuck and decided to check it with an indicator. To my shock, the outer end (about 8") was out by .006"! Moving the indicator close to the chuck dropped the reading to about .003". This chuck has always held work to just under .001" since I bought it new, so I began looking for the error. The jaw gripping surfaces themselves show no burrs or scars.....in fact they still look new. I took the jaw tops off and discovered some minor hardened oil under them from being changed, depending on the work to be done. Okay, using 0000 steel wool and WD40 I gently removed the crud down to the ground surface and reinstalled the tops. Same readings, no change at all. I removed the entire chuck and examined the backing plate/spindle threads. Nothing unusual at all.

    It might be possible (although I doubt it) that I inadvertently switched the jaw tops (or the jaws) at some point. Hard to believe, as I change them one at a time, but it's the only possibility left that I can think of. Could that possibly induce an error? Before I play "swap a jaw" I thought I'd ask and see if anyone had suggestions. If not, it may be my first experience with grinding chuck jaws.

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    Hard to say,but seems you have a chuck with bolt on jaws,rather than inside and outside sets.......anyhoo,my experience of the Cheap Chinese chucks is that nothing is hardened in them,so rapid wear is the order of the day....But any quality chuck ,even Chinese will cost twice what you paid for the lathe.

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    Deleted......double post.

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    Well, since I posted I went back to the shop. I rechucked the bar stock and put the indicator on it. To my amazement, it now reads a solid .002" out to about eight inches and is consistent.....that is, the "high spot" is in the same place. I rotated the bar and tried again with the same results. At this point I'm suspecting my "test bar" which is nothing more than a brand new length of 1" cold rolled bar. I'll look around and see if I can't locate some kind of ground, cylindrical stock and use that. It might be that I took my readings with the compound in a slack condition. This time I made sure that I had positive forward pressure on the compound screw before I took the readings. Actually, .002" error is acceptable for what I do. At any rate, I obviously need a better test bar!

    The chuck is a Phase II, purchased about ten years ago. I remember the ad stating that all parts were hardened and ground and, frankly, it's lived up to that. It has always been babied and treated like gold.

  5. #5
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    Order yourself a piece of Thompson rod, like .500 or larger...shouldn't be too expensive and will be straight as an arrow.

    .625x16.000...22 bucks.
    https://www.mscdirect.com/product/details/60037793


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