Quote Originally Posted by Paul Jones View Post
Marv,
Over the years I have obtained 4-jaw chucks for my Unimat, mini lathe , and 12" geared head lathes and find them very useful. I am now working on a side project to build a small marine compound steam engine that requires four matching eccentrics. I also plan to build more than one engine. I could hold the small eccentrics with a 4-jaw chuck. However, I have modified some plans from Rudy Kouhoupt to build a micrometer faceplate attachment to make it easier. Its purpose is to hold the eccentrics during machining in a known position adjusted by a calibrated screw arrangement and be able to repeat the process. I will make the faceplate with more universal holding capabilities so it has more uses. I will publish photos of the tool.
Thank you for the interchange of ideas, Paul
Sounds neat but isn't the 4jaw in effect a micrometer-adjustable work-holding device?

When I have to do eccenctics with matching offsets, I set up a collet chuck in the mill to hold the parent stock end-up. Center the stock and step off by the offset radius. Center-drill with a tiny (#00 ?) center drill. Mount stock in the 4jaw and, using a wiggler or pump center and a Di in the tool post, get the center-drilled hole running true.

After turning the first eccentric, repeat the process. (A vise stop re-positions the next one perfectly for center-drilling.) If you only slack off two jaws in the 4jaw when removing the first, the second will be almost dead-on when you mount the second.

Everyone has his own favorite approach to production work. All that matters is that you're having fun. And I agree, the interchange is stimulating and, hopefully, enlightening for some of the lurkers who I hope are reading.