Atlas-craftsman 101.07301 Chuck Wobble

Wa5cab
The gap rotates around the spindle as the chuck is turned. In other words the chuck is tight on the spindle and not moving around. The chuck is a 4" 3 jaw Atlas chuck.

Thanks Ed
 
Do you have a faceplate or anything else that fits the spindle? Be sure that there isn't any step in the register from where they faced the flange surface back.

You didn't answer my question about whether or not you had a 4-jaw chuck.
 
Wa5cab
Thanks again, Yes I do have a face plate, there is no gap when I mount it on the spindle. I have noticed that it is not running true, can't recall how far it was out, but it was not just .005 or something it was a good bit out.
When they faced the flange they did it from outer edge toward the center in one pass then did it over again all the way across the flange. I don't see how there could be a step but I will check when I can.
Sorry I did not answer your question, I only have a three jaw chuck and a face plate.

Thanks again Ed.
 
If they didn't face it in far enough, there would be a step remaining.

The threads in a chuck are generally fairly loose. The chuck is centered up on a combination of the register and the flange.

The faceplate can be trued up by simply taking a facing cut across it. However, I wouldn't do that until you are sure that you are not going to replace the spindle.

On your 3-jaw chuck, if it were mine, I would carefully grind about 0.010" off of the thread start. And see whether or not that would get rid of the gap. If it doesn't, you haven't hurt anything. At leas so long as you didn't get the stone into the unthreaded bore.

If you were to get a 5"4-jaw chuck, you can probably check the trueness of the 3-jaw chuck body. Just be sure you don't crank any of the jaws out far enough to hit the bed.
 
Thanks Wa5cab
I will try to get a small grinder and try that, as you said it can;t hurt.
I don;t understand your last statement, would I want a 5" chuck on a 6" lathe ? Are you saying chuck my 4" three jaw in the 5" four jaw and chuck a piece of drill rod in the three jaw to test it?
Thanks again Ed
 
That wasn't actually what I was thinking of. And yes, a 5" chuck is marginally too large for a 6" lathe. However, if you are careful never to run the jaws more than about 3/8" outside of the chuck body, It would allow you to safely chuck a little larger part than you could do with a 4". For example, If you were to chuck a your 4" 3-jaw in a 4" 4-jaw, the jaws might be a little farther out of the chuck body than is good practice. And especially for trying what I was thinking of.

You have been indicating the face of your 3-jaw and apparently finding enough runout that the chuck shows visible wobble when you mount and rotate it. What I had in mind was finding out whether the front of your 3-jaw is parallel to the back, and whether it was parallel to the area around the threads. This would take some time as you would need to make a jaw tension ring to get the 4-jaw's jaws tensioned like they will be with the 3-jaw held in it. Anyway, supposing that you had a 4-jaw, pull the jaws out of your 3-jaw. Turn the jaws in your 4-jaw around so that the tallest part is toward the outside. Temporarily mount the 3-jaw in the 3rd (tallest) step of the 4-jaw and get it roughly centered. Remove the 3-jaw and measure the diameter to the 2nd step. Make a ring of that diameter (you'll probably have to turn the jaws back around). Set the ring against the 2nd step in the 4-jaw's jaws and tighten them. Set up your indicator to read the flats in front of the 3rd step. Set the indicator to zero on jaw #1 and read and record the readings on the other three jaws. Remove the ring and re-mount the 3-jaw in the 4-jaw and center it. Rotate it (if necessary) so that there aren't any screw heads in the way over the spots where you just read the offset of the 4-jaw's jaws. Read and record the readings at the same spots as previously read. If the 3-jaw's back is perfectly parallel to it's front you would get about the same readings as before (if you were using a 5" 3-jaw they would be the same if the 4" is perfect but if you bought a new 3-jaw, I would be inclined to forget your present 3-jaw).. Now move over to the center of the chuck and check the runout on the face that should contact the spindle flange. And check the runout of the unthreaded part down in the hole.

If you actually ever do all of this, at this point leave everything as is and report back.

As justification for buying the 4-jaw, you will eventually need one anyway, regardless of the outcome with your present 3-jaw. ;) Most things that you can do with the 3-jaw you can also do with the 4-jaw. The 4-jaw does some things that the 3-jaw can't. Like holding square or octagonal stock. About the only thing that you can't with it do is hold hexagonal stock.
 
All of that is way over my ability. I haven't cut a single chip sense high school and the teacher just let me play with the lathe then. I think I will just get a 4 jaw and see how that goes. Thanks for all of the help. I think I would have sold the lathe and bought an import.

Thanks to all of you.
Ed
 
OK. You would have eventually needed the 4-jaw anyway.
 
I am thinking that I might just get a 4 jaw and see what I can do with that. I still wonder if I am dealing with both a bad Chuck and a bad spindle. Thanks again for all your help.. Will keep you posted.. Ed
 
Ed,

I would agree. With it (assuming that you get a decent one), I think that you can eventually figure out whether there is a problem with your spindle or not.
 
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