14 years ago
years, and they all sort-of worked. Well, worked better than tapping
dry. What works better than anything else I've tried, at least for
aluminum, is Rustlick WS-5050 emulsion of chlorinated paraffin in water.
Given that I have this stuff in my coolant pump, I always have a gallon
on hand. I just flood the area, and proceed. This while using a
piloted tap wrench in the drill press (or mill).