Another thing to remember when drilling Cu is that you should take a little material and back out... let the temp drop a little and maybe hit it with a quick shot of WD-40 ...then do a little more.
A drill press is a must if it requires a very accurate hole. A mill with a collet system would be better.
If it's vital and going to cost big $ to replace... get it done at a machine shop. At least that way they have the right equipment.
Hope that helps...
