Tapping copper is horrible with small taps. Typically anything 6-32 or smaller is really hard with regular taps.
For one, make sure your doing what uberblue is doing,
secondly. if you got a lot to tap, get ahold of some thread forming taps, also called cold forming or fluteless. They use a little larger hole and you can virtually turn them all the way through the material with a little oil. The only downside is that there isnt as much of threads there. Close but not quite as much. They are typically a little stronger than the same amount of thread with a cutting tap becasue the metal is being pushed and not cut.
I use a 4-40 tap and a #38 drill and I have tapped probably over 100 holes with the same tap. about 90% being in copper.
They can be found at mcmaster, jtsmachine.com and many other places. dont expect to find them locally.
Jon
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