I have a Union brand three jaw chuck that I took a part because of a bad jaw. I checked all three jaws and found that #2 & # 3 jaw have seven teeth and # 1 has eight teeth. Numbers on jaws are #1 D999 #2 D999 #3 D996. Number 2 jaw has four broken teeth. My question is, should all the jaws have the same number of teeth and the same D markings, did someone put wrong jaws in the chuck?
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Chuck Jaw Question
- Thread starter navycwo
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- Mar 1, 2012
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I'd say someone put the wrong #3 jaw in it. Jaws are ground in sets and serial numbered.
As far as the number teeth I assume you're talking about the back side of the jaw where they engage the scroll and the number can vary. As you can see in this picture of a set for one of my chucks the #3 jaw has 8 and the others have 9.
As far as the number teeth I assume you're talking about the back side of the jaw where they engage the scroll and the number can vary. As you can see in this picture of a set for one of my chucks the #3 jaw has 8 and the others have 9.
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The real question is if you chuck up a dowel pin or some other ground diameter, is it centered when you measure it with an indicator? If it is, the rest doesn't matter (except for the broken teeth.)
Since #3 D996 seems to be the wrong jaw, I'm assuming that #1 & #3 should have 8 teeth and # 2 7 teeth.
I understand what you are saying, can't check that with the broken jaw.
If that is true why does the jaws from oldmachinist post above have odd and even teeth.
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The teeth on the back of the jaw are just portions of a gear that mesh with the scroll gear in the chuck. The number of teeth is irrelevant. If you cut a gear into segments some parts will have more teeth than others.
But back to the OP's question yes the serial numbers should all match. Your number 3 jaw is from another chuck, however it could have been reground to suit its place. If it chucks up a piece of round and holds it centralised then its doing its job. But what to do about jaw #2?
Cheers Phil
But back to the OP's question yes the serial numbers should all match. Your number 3 jaw is from another chuck, however it could have been reground to suit its place. If it chucks up a piece of round and holds it centralised then its doing its job. But what to do about jaw #2?
Cheers Phil
Try to find a Union #2 D999 jaw. I know that would be like finding a needle in a hay stack, but I will keep looking. Never know I might get lucky. Mean while I'm looking for a 6" 4 jaw chuck 1 1/2" x * TPI.
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You wont get lucky. The chuck you have has a serial number. There isnt another Union #2 D999 chuck out there. All chucks have their jaws factory ground in their respective bodies for parallelism and centrality. And are then stamped to keep them together. If you sent it back to the factory they could make a new jaw and grind it to suit. The cost for that will be in excess of what a new chuck will cost. The best you could do is find a jaw that fits and grind it yourself. Or weld in some new teeth and machine/grind/file to suit. You will be better off tracking down a replacement chuck. Do you have the other set of jaws for your chuck?
Cheers Phil