Atlas-craftsman 101.07301 Chuck Wobble

Ed,

Short answer is yes, if the 1"-8 female threads on the back of the chuck come all the way out to the surface, they must be cut away. The problem is that the counterbore is what centers up the chuck to the spindle. So it MUST be concentric with the jaws. If the jaws are in good condition, what I would do is to take a piece of precision ground steel solid round just small enough to fit through the hole in the front chuck body and mount it in a 4-jaw and indicate it in to zero TIR. Then clamp the chuck to the round with its jaws.

But before we get into that, it still isn't clear to me whether the chuck is a solid-back, as most were, or has a back-plate. Easiest way to answer that is to take and post rear and side view photos of the chuck. I can't understand why the back of the chuck (whichever variant it is) doesn't have the register counterbore as I can't imagine it shipping from the factory like that.
 
I forgot to add that if the chuck does have a back plate, you could, if you have a large enough 4-jaw or if you can figure a way to solidly attach the back plate to a face plate, do the counterbore yourself. But you would want to confirm that the axial runout of the face plate was essentially zero first. But I think that all around, as you are still working on the machine and don't know how accurate the rest of the machine is yet, you would be better off getting the counterbore fixed on a larger heavier machine.
 
wa5cab said:
....If the jaws are in good condition, what I would do is to take a piece of precision ground steel solid round just small enough to fit through the hole in the front chuck body and mount it in a 4-jaw and indicate it in to zero TIR. Then clamp the chuck to the round with its jaws...
Click to expand...

That's a good way of doing it ! The following photo shows that identical operation on a backplate into which an ER-40 collet chuck has been shrunk. I put a 1 inch piece of drill rod in the three-jaw and then turned it to 15/16 so the diameter is now true with the spindle axis. With a 15/16 collet installed in the ER-40, I secured it over the turned diameter of 15/16 then machined the backplate register. The backplate is shown in a stage of partial completion:

P1020144.jpg
 
Thanks to everyone. For some reason my computer to a strong dislike to Hobby Machinist, it would let me go anywhere but here. When ever I tried it said page not available. Well back now. Thanks for the info, I think I will try to find someone to cut out 3/16 of the threads on a bigger lathe. I would hate for this to be the first thing I have ever turned that mattered. I played with a lathe in high school, but the teacher knew nothing about it and said you can try it if you want, and I have many hrs on a brake lathe. Thanks again, will update when I get this done, will take a little while as work is kinda crazy now. If I did try this how would I center the hole on the lathe? I can see how if it was not threaded but being threaded??? Ed
 
Ed,

I'm not sure that I understand your question. Normally, a back plate is bored out to the minor diameter of the threads. Then it is counterbored to the nominal diameter for a short depth. This larger bore is the part that centers up on the spindle register. Finally, the plate is threaded to a major diameter maybe half a thou larger than nominal, shown in the thread tables as the max major diameter of the female threads.. So the final pass will leave a barely visible score in the register counterbore. This ensures that the spindle register and not the threads are responsible for centering the chuck.
 
Wa5cab My chuck has never been counterbored and because of this the chuck is threaded all the way and can't reach spindle register. I need to take my chuck apart, it does not have a back plate, and attach it to the face plate and center it on the lathe and cut out the threads so it can register on the spindle.
How do you center something that has a threaded surface to measure against? Also is what I am planning to do a good idea?
 
Ed, what's your level of experience? This is something for a well versed amateur or a professional to do. Normally, with chucks that are sold ready to run the purchaser expects a run out of .002 to .003. Do you think you can locate your chuck on a faceplate that accurately? I'd look for help if I were you.
 
I have little to no experience with a lathe. I have a many hours of work on a break lathe, but that won't help much. I just hate to take my chuck to a machine shop and spend $_____ on a chuck that I am not sure will work. The threads were messed up when I got it and I had to chase them with a tap just to get it to thread on at all. Thanks T Bredehoft
 
I made a collet holder for my new lathe, messed up the threads myself. I bored them out, and pressed an insert in, put a couple of 5-40 set screws in the joint between the insert and the mounting flange and chased new threads, with the proper locating collar. You might try that.
 
Ed,

I'm out of town for a funeral and fighting an extremely slow connection. And probably paying roaming charges. So this will likely be my only reply until I'm back in Houston. But I agree with Tom. You need to get a local opinion from someone competent to give one. I can't imagine a reputable chuck manufacturer selling an unfinished chuck. So there is something amiss here. If you can find someone local who is willing to look into it and not charge you more than a decent new (to you, it can be used if good) chuck would cost, he might be able to salvage it. If not, you are probably better off scrapping it instead of throwing good money after bad. I know what I would do but I'm not going to write out detailed instructions as anyone who CAN fix it will know HOW to fix it.

I don't specifically recall which lathe you have and with my connection problem tonight it might take me an hour to find out. But assuming that you have an Atlas built 10" or 12", the factory specs on the diameter of the register are 1.5000"/1.4995". I got that from Jolene last year. Pass that on to whomever you enlist to help.
 
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