Lapping Compounds - What to Use

Discussion in 'Trumpet Discussion' started by Gilligan, Apr 9, 2005.

  1. Gilligan

    Gilligan Pianissimo User

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    Aug 3, 2004
    Colorado Springs, USA
    What is the best type of lapping compound to use for brass instrument valve repairs.

    I've read on several sites that a garnet compound is best for working with brass on brass.

    Will this work for valves and is this also good for slides that have a nickel outer sleeve? Also what grits are the best for each job?
     
  2. Robert Rowe

    Robert Rowe Mezzo Piano User

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    Dec 24, 2004
    Forget it, man.

    Leave that for the pros (certified band instrument repair technicians).

    (A tip -- "lapping" removes material. Removing material from any part of a horn should be considered a "last resort" procedure).


    Robert Rowe
     
  3. old geezer

    old geezer Pianissimo User

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    Dec 26, 2004
    Indianapolis,In.
    if you insist on trying to do a very little lapping to free up your valves - use a non-gel type tooth paste. go in from the bottom of the valve and use the corresponding valve in each each valve casing. like Robert said -let the trained tech do it, but if you do it ,tooth paste works well for the amateur.[it takes off very little but you can still mess up a horn] old geezer Dave
     
  4. gzent

    gzent Fortissimo User

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    Nov 5, 2003
    Rochester, MN
    OK, wouldn't it make more sense for an amateur to start with a compound that is not abrasive at all? Because, if a valve is sticky because of corrosion or deposits on the cylinder wall then removing the foreign matter first before the metal would be preferable, wouldn't it?

    I guess I'd try a mild, nonabrasive chemical varnish stripper first before lapping. Actually, I wouldn't, if it was a valuable horn I'd take it to a pro.

    Greg
     
  5. Robert Rowe

    Robert Rowe Mezzo Piano User

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    Dec 24, 2004
    Greg --

    Yes, and no.

    First thing to do with any horn with problematic valves is clean the horn internally with mild detergent-type cleaners (I won't get into which are the "best" ones ...).
    Generally, there will be something "out-of-whack" with either the valve piston or the valve casing. In this case, a professional tech will know what to do (he will have specific-sized mandrels for the horn to effect this procedure, and sight along a leveling block to straighten the piston).
    Ususally, some force or shock to the horn (such as "knocking" it into something, dropping it, bumping it, etc.) will transfer a stress to the valve casing &/or associated "knuckle", causing a "bind", or "torquing".

    Again, and I can't stress this enough -- "lapping" removes metal.
    Don't think that "hand-lapped pistons" as you see advertised is so wonderful, and so "hand-made in America", or some-such. The last thing you want to do (when all else fails) is remove metal. When it is gone, it is gone.

    Much of the problems in this area (and just about any subject area), is we are looking for a "quick fix", or "magic pill", or "magic bullet". Screw that !! Remember the slogan about "the old-fashioned way" ?

    Proceed at your own (or the horn's) peril ....


    Robert Rowe
     
  6. mike ansberry

    mike ansberry Forte User

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    Dec 30, 2003
    Clarksville, Tennessee, U
    With some of the cheap horns going around today (and some of the big name brands have some cheap stuff on them) the metalurgy (sorry about the spelling) is wrong in the alloy used to make the valves. If the alloy has too much tin in it, it will "gaul" with the casing. (When you rub like metals together they stick to each other) The evidence of this is brown places on the valves. If this is the case, you can take a rag and some lava soap an polish the brown spots off the valve. Of course the problem will return with time.

    The Jupiter corporation admitted this problem, and has sent out replacement valves to all who have Jupiter horns with this problem. This has really made me a fan of Jupiter. The had a problem, admitted it, and took care of it. I can name at least 2 major inst. makers who have the same problem, but are denying it and not taking care of their customers.

    But like Rob said, the last thing you want to do is actually lap a valve. Once you take off too much metal, it is really hard to put it back, and not cost effective.
     
  7. gzent

    gzent Fortissimo User

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    Nov 5, 2003
    Rochester, MN
    Robert,

    Yes, I guess I forgot to mention the 'deformed' valve case possibility as well.

    That's probably the most common cause of sticky valves I would think. Either from dropping, bumping or over aggressive cleaning pressure on the slide puts a slight deformation on the case which 'pinches' the valve piston and viola! you have a sticky valve.

    I agree - if cleaning doesn't fix a sticky valve take it to a good tech - the case is probably out of round.

    Greg

    PS - Are you are a trained tech, just curious?
     
  8. Robert Rowe

    Robert Rowe Mezzo Piano User

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    Dec 24, 2004
    Yes, Greg -- but it is an "on-going process" -- I will never know what I would like to know about band instrument repair. My business-partner is a prominent luthier (string-instrument repairer/builder, who has restored legenday instruments that are in the Country Music Hall-of-Fame Museum, and has worked on Keith Richards' ("The Rolling Stones") guitars. My wife is a grad of Red Wing Technical College Band Instrument Repair school, just East of you, on the Mississippi. Not surprisingly, most of our work is on guitars, and my experience goes back many years. We also work on woodwinds, percussion, instrument cases, amplifiers, P.A. systems. We are presently expanding into a much larger facility, as we formerly had a small "home" shop. I bought-out a West Coast brass and woodwind repair shop, and I still have to inventory everything and find a place to put it.

    Regards,
    Robert Rowe
     
  9. Tootsall

    Tootsall Fortissimo User

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    Oct 25, 2003
    Yee HAW!
    I had this same problem with a) Kanstul (Besson International), b) Yamaha (YCR 2330), c) Bach 180-ML 37, d) Schilke (B1), and e) Jupiter 846L. Brown spots that looked like "varnish" showing up on the valves and that required the use of a cleaner to get it off. I used a stainless steel pot cleaner developed for highly polished stainless (Lagostina).

    The final solution to the problem was to change valve oils. Have never had a recurrence since then.

    FWIWCFM
     
  10. Robert Rowe

    Robert Rowe Mezzo Piano User

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    Dec 24, 2004
    Ed -- you were previously using Al Cass, correct ?

    Robert Rowe
     

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