new 3 jaw chuck, now what?

Chuck Lippmeier

I'm hopeing for some advice from them that's been through this before.

I ordered and just received a new 3 jaw chuck and backplate from Shars. They came in seperate boxes so I tried to bolt the chuck to the backplate. They won't bolt together right. There is a concentric step at a diameter inside the bolt pattern that rises about 0.1 inch on the backplate and what I assume is supposed to be a matching step depressing down into the chuck. The problem is that the diameter of the depresion into the chuck is slightly smaller than the rise on the backplate. So, when I try to bolt them together they won't come together.

The only thing I can think to do is mount the backplate on the lathe and turn down the rise until it fits in the chuck. Somehow this goes against what I would assume to be the right thing to do to a new part but I'm thinking it might be standard practice to get a perfect alignment on my lathe.

Should I return the shipment or turn down the backplate?

Thank you,
Chuck Lippmeier

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