Not meeting in the middle

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Haynie

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I have an Enco mill drill lathe combo. The three jaw chuck it came with needed a cleaning so I took the chuck off. I made sure the jaws came together and they did for the most part but I was pretty sure there was crud keeping it from coming together completely. I marked where each jaw went then took them out. I cleaned everything as best I could with a wire wheel and a wire brush. There was a LOT of crud in the jaw teeth. When I went to put them back in I put the jaws in the spaces they came out of and screwed them back in using the same slot I had used to take them out. After lots of tries they will NOT meet back in the middle. I have moved the jaws around, I have used different tightening points and they will not meet in the middle. The jaws are not always the same distance apart.

I can vary the distance apart they are but they NEVER meet in the middle. Any suggestions?
 
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When you say they don't meet in the middle do you mean by a few thousands of an inch, or are you saying .050 or .100 for example? Any chance of a picture? It could be that it is a poor quality chuck, someone put the wrong jaws in it or the carriage or tool holder was run into it resulting in a bent jaw from the crash.

A better test is to put a round rod in the chuck and with an indicator on it, rotate the chuck by hand and see how much run out (wobble) there is. If it is within a couple thousands of an inch it doesn't matter if the sides of the jaws all touch.

It is possible to reface the insides of the jaws if they are out too much to make it grip true to the axis of the lathe but lets see what is going on first before going there.
 
Here is a pic of the space. I think this will definitely cause run out. I am sure it is not a great chuck but it has worked fine until I took the jaws out to clean.
 

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Maybe you have already done this, but check again.
Each jaw is numbered to match a numbered slot. Start with #1 jaw in #1 slot, move around to #2 and so on, in sequence. It looks like one or more of yours is out of sequence.
 
I had to figure this out once when I tried to chuck up something with too large a diameter and they all fell out. I found it easiest to take the chuck off the lathe and lay it flat on a table. With none of the jaws in place rotate the part that makes them move in out and watch the rotating thread that moves the jaws. You can position it so the thread is just about to pickup jaw 1 and then put that one in place...then rotate it around to just before jaw 2 and slide it in place....then repeat for jaw 3. For my chuck the problem was my jaws were labelled but the slots they slide in weren't so I had to try a couple times before they met up correctly.
 
Got the jaws in the wrong slot, as mentioned above there should be numbers 1,2,3 and you need to start with jaw 1 and put it in slot 1, then 2, then... you get the idea....
 
Thanks. I will look for numbers. Like I said I marked them before removing but it messed up.

I will give that a shot gil.

Anything helps at this point.
 
To me, it looks liek the one that is the furthest out in not starting on the same postition of the gear that the other 2 are. I have run into this before. Try removing them all again and try to start them all in the same position. Looks to be offset 1 revolution
 
I agree with the boys. You just need to get the sequence right.

Sent from my iPhone using Forum Runner because I can't reach my desktop!
 
I agree with the rest of the guys.....you may have marked them perfectly fine but the PO may have taken it apart and not replaced them in the sequence mentioned above....worth a look to make sure...
 
Yep, they were numbered. Little dots, and not in the order of where I marked them. After they were in the right order they still did not come together right. I tried Gil's method and they closed but looked a tad off. I reinstalled the chuck (Little dots to line up there too). I don't know what I did but like magic after I took the jaws out again and replaced them they came together perfectly. I checked for run out and 6 inches from the chuck on a SS brand new propshaft there was no run. at twelve inches I had less than .001. I'm happy.

Thanks folks.
 
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