High precision lathe chucks

[chris m]

Good morning

 

I have a workholding application that I'm working my way through and I am looking for some insight to keep from just going back to what I know. The application is opening the bore of an existing part, chucking on the datum surface of existing part, which has very good precision on both size and roundness. The roundness requirement for the boring of this pretty flimsy part family is .0002" max, concentricity is the same. Currently we are using a Positrol hydraulic membrane chuck with a segmented collet for this application; accuracy and roundness are excellent with this method, but chucks / collets aer brutally expensive [like $3000 a collet] and setup times are longer than I would like due to the necessity to change chucks for big variations in size and the duration of the "truing up" process that results.

 

My first thought for "fixing" these issues is a 3-jaw or 6-jaw quick-change air chuck from someone like MicroCentric. Changeover time is much lower and top tooling is cheaper, but I am worried about chucking distortion with a jaw chuck. We own a couple of these chucks and they work well, but once your requirements for roundness get down below .0002" they start to struggle. A diaphragm-style chuck would likely do better for roundness, but changeover time and expense of top tooling goes up, I think anyway.

 

Suggestions / thoughts?

[Guest CNC Apps Guy 1]

Hainbuch is my favorite. ATS reps them here in SoCal. They have about the quickest Change-Over I've ever seen, and CERTAINLY that fastest I've ever used.

[Dave.L]

quote:

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Hainbuch is my favorite. ATS reps them here in SoCal. How is a 3-4 second changeover?

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We use Microcentric, knock offs of Hainbuch. Good but for what you explained, I don't think they are good enough.

 

Based on the thin wall and .0002" you spoke of, I think you will need air chucks. They are more accurate than hydraulic but they come with baggage too. You will need to run some plumbing.

[chris m]

Gripping diameter (OD) ranges from 60 - 160mm, so collet-type workholding like that Hainbuch system is impractical. Those chucks are pretty sweet, though.

 

Dave, we have MicroCentric Quick Change Ultra Precision 3-jaw air chucks in a couple of applications right now, unfortunately one of the chucks is used-up to the point that it won't do what I want and the other is in an application that I can't break into to test.

 

C