Lathe Chuck Questions

[rommel]

A few questions for those in the know about machine tools: A couple of years ago, I picked up a mid-60's (I think) 16 x 78 Axelson lathe that came with a 12" Cushman 3-Jaw chuck. The chuck will stay true for whatever size I grind the jaws to, but it'll be off by anywhere from .005" - .030" when I try to hold any other size stock. I've cleaned the scroll, ways and jaws time and again, but it doesn't help at all! I'm getting tired of grinding and re-grinding the jaws everytime I want to do any precision work.
1) Am I correct in figuring that the scroll is worn out?
2) Does anyone have suggestions as to where to start looking for parts or reconditioning services?
3) Does anyone happen to have a decent 12" 3 Jaw with a D1-6 backplate lying around that they want to sell cheap?? ;)
4) Any other ideas?
Thanks in advance for your help and input!

[hoeker]

many lathe chucks are adjustable, there are normally 3-6 bolts in the face, then 3 to center the chuck. if it's not adjustable you may be able to remount it and correct the problem.

FWIW, most shops that need precision turning done on manual lathes use 4-jaw chucks.

[partybarge_pilot]

Sroll is hosed. People like to torque on the t-handles with cheater bars. This can bend the ribs on the scroll. Or it was used for 1 dia. a lot and has worn flat spots. Check the freeplay in the jaws at different spots on the scroll. If it varies more than a couple thou buy a new one.

[FABRICATOR]

I have used old machinery for many years including some that are O/H belt drive! I use a 17” Sidney lathe from 1905 for wheel work! The fact that you grind the jaws and it runs true does not mean much. This would work no matter what was bent or crooked. You need to see first if the headstock shaft, chuck mounting plate, and chuck, are running true, in that order, with a dial indicator. If the chuck is as old as the lathe, you would be better off finding a newer one. The jaws can also get loose in their slots. A large 3 jaw standard chuck needs to be in very good condition to routinely grab things and have less than .005” run out. Ebay is a good place to find this kind of stuff but watch the shipping. Good luck with bargains on D1-6 as it is probably the most popular of all mounts.