How to center a piece of work on a rotary table?

[Hawkeye]

Ok, Ron. Looking at the drawing, Stan's tooling plate and my centering point will do the job. Mark out and punch the centre points for the 4 through holes and the centre of the concave curve. With the rotary table accurately centred under the spindle and the DRO zeroed, clamp the tooling plate to the RT. The plate should have enough threaded holes to clamp the work piece in a variety of positions.

With the centering point in the spindle, place the work on the plate and bring the point down into the centre for the concave curve. (At least that's where I would start.) Clamp the spindle in that position to keep the point in the punch hole and rotate the work to line up one of the straight lines for the concave section with the X or Y axis. Clamp the work firmly to the plate, leaving the first working section clear. You can then cut the concave section.

Pick an outside curve and move the work to that centre, again using the point. That's where the zeroing of the RT comes in - lets you go back to 0,0. Again rotate the piece to align a flat side with X or Y. Cut, move, repeat.

After the top side is complete, the centering point will help you line up the piece to counterbore the back side.

At least that's how I'd do it if I couldn't use my CNC.