Posted by Bill V. on December 12, 2003 at 03:02:45:
In Reply to: Lapping of Valves posted by Jim on December 11, 2003 at 23:55:22:
Lapping of the valves in repair/mechanical terms is to put a libricated fine grit type of stuff (known as lapping compound I think) on the piston and move it back and forth through the cylinder. This is what is done to ensure smooth action and a tight fit. That's why my repair guy told me when I just had anew valve put in an old sousaphone. Work's perfectly now. Makes me want to go get two more new ones to replace the old ones.
Coincidently, they use this same technique to lap valves for engines and that sort of stuff. I once did a google search on "lapped" and "lapping" and came up with that sort of stuff. Nothing about brass.
Hope that helps you out too!