Old chuck jaw refreshing

[jwmay]

Well it seems like every thing about this chuck is out. .008" out on the face, .011" out on the diameter, and today after cleaning the jaws ways it's .008" out at the jaws. So....

 

[ErichKeane]

Typically the face is surface ground square to it's back, so I would expect the problem is the backing plate. You might be able to put it on a surface plate to measure it (or try indicating in the backing plate).

 

[jwmay]

I'm just playing anyways. This chuck has integral threads. I kind of thought maybe cleaning up the register end may have been the better strategy. But it was found in the bottom of a drawer in a garage of a man who'd passed a decade earlier. It was seized shut, rusted beyond identity, and literally buried under junk. Then a man full of ignorant enthusiasm found it. He electrolytically derusted it, he torched it, and he put a 6 foot long bar on the jaws in a fruitless attempt to unstick it. Eventually he gave up and decided upon a destructive autopsy. Step one: Drill holes in it at random locations to see what's inside. Right about that time, with the 6 foot bar on it, he gripped the nut on the back of the chuck in a vise, and that nut unscrewed painfully, embarassingly, and shamefully too easily. Thereby releasing the jaws from their death grip on nothing, and hanging a weight of shame around my neck for all time. This was before I'd gotten involved in the forums I guess. So, like I said, it's pretty much ruined. May as well try something I normally wouldn't, and see if there's a lesson for a knucklehead like me to learn.

or try indicating in the backing plate).

And yes, the back of the chuck wobbles too. But seeing as how I don't ever use that side of the chuck, I don't care. This is like an "in case of emergency break glass" type of chuck. Lol Or then again, it may be a "put it back in the scrap bucket" type of chuck ". I'm not certain either way yet. But I am kind of enjoying myself so far. That was kind of the point. Rest assured, I've abandoned the shenanigans of my early days. I ask many questions about presumably simple things now, to avoid wrecking something else. Other than a zamak gear and this chuck, I've not ruined anything else. Lol

 

[mikey]

Other than a zamak gear and this chuck, I've not ruined anything else. Lol

The day is still young and the years are long - plenty of time to screw up! I could write a book on the number of mistakes, assumptions and transposed decimals I've done - and I've been called out on a number of them by some of our guys - so just enjoy the hobby and keep learning. I've heard that at some point in time our successes begin to outnumber the mistakes but I've not been able to confirm it!

 

[graham-xrf]

And yes, the back of the chuck wobbles too. But seeing as how I don't ever use that side of the chuck, I don't care.

Having regard for the wobble is not about whether one ever uses the back of the chuck. It is about appreciating what it is telling you!
There was a stage in the life of the thing when that part was in a lathe, and was cut circular without the wobble.

So, let's assume that the end of your spindle, and it's register face, without the chuck present , does not have a wobble.
Start with the backplate. With clean threads, and no burrs, the backplate should screw on until the register face finds the face on the spindle. There is not a whole lot that can happen to go wrong there unless the whole thing took an axial whack enough to bend it into wobbly wheel state.

The whole rest of what the chuck can ever do requires, at least, that this part runs true! So if it does, then something in the rest of the chuck has a problem. If it does not, then the rest of the chuck may be blameless, and should not be "worked on" at all, until the reason the back is skew has been found. Even a small burr preventing it from bottoming properly when being screwed on, can mess it up!

 

[jwmay]

Start with the backplate

I think you're right. Except that there isn't a backplate. And I have firsthand knowledge of incredible forces, temperatures, impacts, and twisting moments being applied to this chuck. Lol
The chuck is three piece. Internally threaded shell with tee slots, a scroll with knurled ring which fits behind the chuck face, and a nut to hold the two halves together. The "back" of the chuck is, sort of, floating. It's literally held on with a nut, and must be floating in order to turn the scroll. In smaller versions, there is a c clip holding it on instead of a nut. So my options were to mill the threaded boss parallel with the face, or turn the face parallel to the register. Having turned the front face parallel to the register, I could indicate the rear of the shell, and upon finding a discrepancy there, turn that portion parallel to the face. This would influence the runout of the rear portion of the chuck, as they are only held loosely together by a nut. But they aren't bolted together, as in a typically constructed chuck. And either way, having done nothing to the chuck jaw ways, turning the face parallel has changed nothing about the axis in which the part is held. It may very well be that the chuck still holds parts "crooked" in relation to spindle centerline. Does that sound right?

 

[chatter chatter cut cut]

tool post grinder. dremel with keystock strapped on with hose clamps . run lathe at high speed with jaws open partly. take small cuts. when all three jaws show bright take 2 or 3 finish passes. whats to loose.?

 

[jwmay]

. whats to loose.?

20 minutes? Lol oh and the cost of a tool post grinder for something I literally dug out of my own trash pile.

 

[jwmay]

Well the used chuck I bought from Ebay arrived a couple days ago. It was pretty much a train wreck. It wouldn't thread onto the spindle at all, so I ran a tap through it. That fixed that. It has zero runout at the face of the chuck, but the jaws don't hold stock well. It's pretty well unusable. So here I am-$160 down the drain for a chuck that is exactly what I wanted... except useless. Lol. So now I have two junk chucks, and two good chucks. So what to do? Toss out all and go buy the darn $500 Bison? Or buy the $500 Dumore? Looks like I will be doing some grinding and some soft jaw making I suppose.

 

[jwmay]

The new old chuck is at .0035" runout after an all night "grinding" session. I checked it with 3/8, 1/2, and 5/8" round stock. Here are two devices I made to put pressure on the jaws, which I screwed up. I ended up using three neodymium magnets between the jaws. But I did a LOT of machining and scratching my head before I came up with the magnets. I stopped grinding as soon as I could tell the wheel was hitting all three jaws full length. Thanks everyone! Maybe tomorrow night, I'll work on the chuck this thread was about.