Bronze can be a realy tough material to work with.
Taps are a kind of voodoo. I have had tap companies come and demonstrate their taps out and as soon as the engineer leaves the building the taps start f'n breaking.
2flute spiral taps are always a saving grace. I can get an aluminum 2flute spiral tap to work on most metals (the engineer still tells me it won't work! Well for not working I got it to drill 320 holes in 410 stainless plate)
On the negative side they wont do well in bottoming holes. especially a .201" deep one, as the point on the flutes is longer than this.
I have recently started using a tap with alot of promis and its an xl from a company I can't remeber. If someone more knowledgable hasn't givin you some magic bullet by tuesday I will post the name of the tap.
one thing that makes life realy easy as it gives the tap a little extra durability is a floating tap holder. I get about 2-3 times the life out of a tap if I use one.
hope this helps
thanks
Michael T.
"If you don't stand for something, chances are, you'll fall for anything!"