Interestingly (well at least to geeks like me) the rotors on the old Elkhart Conns were not lapped, they were just machined to fit correctly. That's probably why they were so dependable. Over the last 20 years or so, a lot of horns have had trouble because they never got the lapping compound completely out at the factory. That would make the valves and the tuning slides stick. The solution for those horns was not more lapping. They were already getting lapped more and worn out more every time you played something. The cure was just to clean them out correctly. I'm trying to remember a time when I ever had to lap a rotor, other than when doing a plating and refitting job. I don't think I EVER have in the last 30+ years on a horn. A couple of times on trombones after the slide knuckle got the crap bent out of it and badly distorted the casing. Very rarely (counting on both hands but no toes involved) I've had to refit the top bearing plate on a new horn when it would fit too tightly and bind the rotor. I do a LOT of lapping for valve rebuilding. Boy is that a tedious job! Apprentices wanted. Must be willing to eat gruel and lap valves 18 hours each day.
- Steve Mumford _______________________________________________ post: [email protected] unsubscribe or set options at https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/archive%40jab.org
