For what it's worth, I never heard though from any technicians I used and I never have lapped a single valve. When I have heard it suggested is when the valves are replated, or the valves never fit right to begin with (valve transplant). Even in the odd occasion where it was suggested to me on a factory horn (once), it was only done once, and it was on a Holton. My Schmid/Paxman valves have never been lapped once as far as I can tell, and I usually just give them a change of oil and soap/water bath every 6 months or so anyway. It's pretty useful to know how to do that on your own, but without the proper tools or the proper technique you can really make some mistakes. -William In a message dated 2/3/2011 5:50:53 A.M. Eastern Standard Time, [email protected] writes:
>> I've never seen such a split on this issue before. Either people advocate it as a last resort, or never even talk about it even in hushed tones. << The problem is that so many technicians who do not really know what they are doing or are lazy just reach for the cannister of lapping compound for every sticking valve. Because lapping removes metal, and because the tolerance of your valves is critical to the performance of your horn, indiscriminate lapping can cause leaking. Lapping has its place. It is used to remove a precise quantity of metal between two mated surfaces so that the tolerance is exact. It's not really a last resort. "Gee, I couldn't get these valves to work right so I just lapped the heck out of them" is not really good practice. Nor is it a first resort. "Sticking valves? Ah, just lap the things." It should only be done when the tolerance between two surfaces is too small. If that tolerance is due to dirt, grime, sludge, calcium carbonate, or other build-up, then that junk should be removed by chemical or ultrasonic means, not by mechanical means. If the tolerance is due to the actual fit of the metal parts, then lapping is appropriate. Making the situation worse is that so many technicians who don't understand the proper use of lapping compound also do not understand the need to completely remove the compound from the instrument, leaving abrasives in the horn. It's all about knowing WHEN to lap. -- *Regards, Dave Weiner Brass Arts Unlimited* _______________________________________________ post: [email protected] unsubscribe or set options at https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/valkhorn%40aol.com _______________________________________________ post: [email protected] unsubscribe or set options at https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/archive%40jab.org
