Nitric acid is kind of hard to come by. I remembered that trick from TMBR but couldn't find it or remember what the acid was. Now that ffkiwi has said what the acid was it's easy to remember the "chapter" was labeled "removing small taps from aluminum" and radiator shops use it. That's the frustrating part of those books. Filled with great info in a haphazard fashion. BTW, those books should be renamed. The Machinist Toiletside Reader. That's were all mine were read.
Bruce, I'm ready now to toss all my cheap bits and buy some good ones. Any ideas about what I should be looking for?