Brad point drills work well in copper. Nothing wrong with the boring head idea.

regards Martin

3/4"Wedon shank 1"rotabroach. A 2MT holder in a drilling machine. You then can do holes from 11mm up to about 1 1/2" with ease. You do need slow speed though. Noel.

Although the copper may be a bit thick I would consider using a piercing saw with a thin blade (less metal to remove). You will break blades but that is to be expected. Finish off with a small half round, or round, file ideally one that has no been used on steel.

I have happily cut 1/8" thick brass with a piercing saw and made 1/32" thick copper gaskets using the above method.

JA

A sharp Q-max cutter would do it. The Deluxe version has a hollow hydraulic cylinder That develops about 5Ton pull – easy to use on the bigger sizes ! Where are you ? Noel.

How about clamping it between two pieces of plywood and using a hole saw?

Mark P.