Truing up chuck jaws

[Moses Weisberg]

I have a pair of Nova chucks, a 1-8 threaded Midi that I started out with, and a 1-1/4 threaded Supernova that I now mainly use. I changed lathes since I got the first one, so I use an adapter for the Midi (the thread inserts aren't exchangeable for that one).

The problem I have though is that the Midi doesn't run true. The runout on the chuck body isn't significant, but the runout on either the slides or the jaws seems to be causing the problem. Since the runout isn't unique to one set of jaws, I'm guessing that the slides are bad. I tend to use this smaller chuck with pin jaws only. I'd try to true up the slides, but I don't want to mess with the top portion where the jaws screw on.

I'm thinking about permanently mounting one set of jaws on it and grinding them true on a metal lathe with a toolpost grinder. Does anyone have experience with this sort of thing?

I could also take this opportunity to make a custom set of jaws dedicated to this chuck. I haven't decided one way or the other, but I'd welcome suggestions on what sort of jaws you would make if you could (I'm primarily a bowl turner).

I'll post pictures if/when I get around to trying this.

[Bill White]

Kinda dumb questions here. Are the jaws in correct sequence? Have ya tried moving 'em around? Just 'cause I don't know.....
Bill

[Roger Chandler]

If you ever had the chuck apart, and did not get the jaws set in the scroll gear correctly, then you would have at least two jaws that would not be true...........the proper jaw on the jaw slide, and the slides placed in proper relation to the scroll gear are what makes the whole thing work.

Sometimes in cleaning out a chuck and relubrication, the wrong jaw slide can be put in the wrong sequence and that will take it toll on being true. If everything is where it should be, then send the chuck back to teknatool to have them make it right.

[Moses Weisberg]

Its always a good question to ask at the beginning. The jaws are in order and on the correct slides. Even when I grip a test bar with the slides alone, I get runout. The jaws run true on my other chuck.

[Roger Chandler]

My guess is that the problem is in your insert adapter and not your jaws since they run true on the other chuck. What is a very small amount of run out on the insert gets magnified out a couple of inches farther out. I would guess that if you have an aftermarket insert and not a genuine teknatool insert it is the problem, and sometimes the teknatool insert can be the issue.

We have seen this kind of problem spoken of before in the forum and others.................try a new insert before you start turning away metal on your jaws.......once you do that there is no going back, and an insert can be had a lot cheaper then jaws...........I think it is likely that one of your inserts is not running true, and that is creating your issue.

[Moses Weisberg]

That would be one of the first places I'd go, but in this case, the insert adapter is fixed into the chuck with a snap ring from the factory.

The adapter I'm using to change from 1-1/4 8 to 1-8 is running true.

I'm really considering sending the chuck back to Nova to have them sort it out now before taking metal off. My guess is they'll be more amenable to helping me if I haven't mucked around with it first.

[Michael Mills]

Unless something has changed I thought the mini was direct threaded and was not made to take an insert? Nova inserts are made to go from spindle size to 1-1/2 (inside the chuck body). I have never heard of an insert for the midi; an off-brand insert?I suspect, if it was running true before then something changed other than the chuck.
When you installed the jaws did you leave them about ¼ turn loose, then scroll in for the jaws to align, then tighten the screws? I believe the jaws are cut from a turned billet so scrolling them in should put them into alignment. At least this is what Nova says to do.

[Richard Allen]

As maddening as it appears, it doesn't matter. Just mark your workpiece so you can remount the workpiece in the same position. Marking your workpiece is a common practice as the jaws will almost certainly crush the workpiece tenon more on one side that the other.

[Russ Massery]

I just received a refubed Supernova2 and set it on the lathe the afternoon. And was rather amazed how much runout there is. Both Radial and lateral runout. I know it's the chuck or the adapter. The stock faceplate runs very true. Thinking of send it back. I'm going to bring an indicator home tomorrow to take some readings. I'm thinking it might be the adapter.