- Which kind of drill do you use ??
Carbide, Coated carbide, HSS
- What is the lubrication ??
Cutting oil, Emulsion oil, Dry
For the drilling, there is two case:
If the lubrication is oil, a standard carbide drill works(be careful concerning the cutting oil, it can oxyde copper). It's better if the helix angle is 30-35°.
If the lubrication is emulsion use coated carbide drill with a low friction coefficient coating (DLC as exemple)
Don't hesitate to use pecking cycle.
For the tapping roll tap is a good solution when material is difficult to cut and soft.