[69_Goat]

I wish I'd seen this earlier.
When you are drilling these holes, use a cutting fluid to provide some cooling for the drill bit and work piece. Any kind of light oil or even just water will do. It'll reduce the chances of the copper sticking to the bit, which is probably causing the breakage.

[Buckeye]

Originally Posted by 69_Goat

I wish I'd seen this earlier.
When you are drilling these holes, use a cutting fluid to provide some cooling for the drill bit and work piece. Any kind of light oil or even just water will do. It'll reduce the chances of the copper sticking to the bit, which is probably causing the breakage.

Good call on the oil, didn't think of that when I drilled mine.