Bruce Barnett wrote in news: snipped-for-privacy@grymoire.com:
Bruce and Darrell are absolutely correct, but I believe you also asked whether a wood tap could be used to tap metal and if a metal tap can be used to tap wood. A metal tap can always tap wood as far as I know. The metal is much harder than the wood. The ability to cut quality threads probably depends on the kind of wood and the pitch of the threads. Wood taps are designed to tap wood. I have never tried to tap metal with one. I expect they would tap lead, copper, bronze, and brass, but I wouldn't use them on steel. Regards, Hank