Circular hole pattern help

[steamer]

OK....take pictures!....

Dave

[Pete49]

another ti if you like. Try Marvs site as I'm sure I saw a rogram for that purpose. But don't hold me to it I'm  and forgetful 
Pete

[Mainer]

To ensure concentricity and solve the clamps-in-the-way problem, I have on occasion clamped a block of aluminum to the mill table, bored a snug sliding fit pocket for the cylinder head, not quite as deep as the cylinder head, and drilled/tapped a couple of holes next to the bored pocket such that the heads of binding--head (i.e. large diameter head) screws will overhang the pocket. Drop in the cylinder head, then thread in the screws and tighten down so their heads hold the part in place.

[steamer]

That's the fixture I was thinking of Mainer....but there are other ways.....

Dave

[rleete]

I made an arbor that holds the cylinder.  No pics yet, I got sidetracked making the nudger that Bogs posted.

Still haven't drilled the holes, but I am doing machining for the first time in months.