[HELP] Centering on a rotary table

[Dan Boy]

Hi guys, as the title suggests, I want to be able to center a part on my rotary table to mill a groove for an o-ring. There must be a way, an easy way to center the part. I just can't think how I am going to do it.

I had thought I could use a DTI on the center of the part but positioning the part accurately will be difficult.

Any thoughts?

Cheers, Dan.