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Discussion in 'Trumpet Repair and Modification' started by roltrumpet, Nov 16, 2009.
What is the best household method for lapping piston valves?
One time took my Bach trumpet apart and put tooth paste all over the valves and then I took off the finger buttons and put the stem in the electric drill. I put the valve in the bottom of the casing and put the drill on full speed. When I was done, the valves were super fast and I never had the popping sound problem when I didn't get a slide in fast enough.
OK, I'm afraid to just leave this without saying it's not true and don't do it.
There's nothing you should do at home along this line -- that's what professionally trained repair technicians are for. The metals involved are way too soft to experiment with -- there's too much potential damage you can do to your trumpet if you try it at home.
Haha I was just thinking about using 60 grit sandpaper on a dowel rod but didnt think that would be enough.
Nobody laps valves that way at all, period, end of story, full stop. We in the repair business use special lapping compounds and lap the piston and the casing so that the fit is just right.
If you have a problem with a piston, take it to your local repair shop. If you don't know of one, you can go to Home Page and click on the Tech Locator link to find the closest technician who is a member of NAPBIRT. It won't give you the full story, though, because there are some fine technicians who aren't members of NAPBIRT.
I lap valves only as a last resort. Most of the time the valves just need a good cleaning, or the casing or piston needs straightening. Even if there is a dent in the casing I don't lap. Those can be hammered out as well.
I too would caution against anything at home.
I have lapped my own valves but I have 40 years of engineering experience building aero and automotive engines and I took some pre-advice from a appropriately trained trumpet repair tech (who knows my background) before attempting anything.
It's simple take notes if you like ..... it is so easy to take metal off and no way to put it back on when you have gone too far ..... and then your trumpet is just JUNK. And that's "Fair Dinkum" (as we Aussies say).
Drive to a reputable dealer.
If you have to ask the question, you have no idea what you are getting into and no idea what you can mess up.
If used valves need lapping, something else is SERIOUSLY wrong. They are lapped at the factory and wear further after that. Relapping would only remove MORE material making the fit even sloppier.
A technician would only do this as an absolute last resort: concert in 2 hours, valve hangs seriously. In any other case, they would try and solve the problem mechanically.
To get residue off of valves (caked on grunge or leftovers from petroleum based oils I use acetone - being careful that it does not get on the lacquer if the horn is finished that way!
Usually when valves hang its because of excessive wear, or something is bent....(a third slide gets knocked etc)....I can't tell you how many times an old horn I'm working on just needed a slight straightening of a slide to get a sticking valve to work properly.
Look and see if from a top and side view if the slide on the valve with the problem is straight...If not...That's probably the culprit. If it was a cheap old cornet like I play with...you could try fixing it, but unless you've been to school on how to fix instruments, It would be best to take the horn in to a reputable shop, and have them look at it. Chances are more damage will be done by messing with it on your own than taking it in and paying a reasonable cost to have it fixed.
"Proper" hand (not machine) lapping is done minimally as part of the re-fitting process of newly re-plated valves and honed casings, to make sure that the tight new valves operate smoothly. Kind of like breaking in rings on a new engine.
My advice is to take it in and give it to a professional to fix it.