lapping valves

Discussion in 'Trumpet Discussion' started by alant, Aug 15, 2011.

  1. alant

    alant Pianissimo User

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    Aug 18, 2009
    Rochdale UK
    Hi i have had problems with a thirty year old strad cornet i recently purchased. The valves are stickig slightly i have been offered free valve lapping should i accept? i have done all the work i can myself cleaning etc.
     
  2. jiarby

    jiarby Fortissimo User

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    Not too much profit in doing free valve lappings for people...
    What's the rest of the story?

    Who is doing it? What method will they use? What material & tools? Are they experienced? Are there recommendations from other people that have had this guy do this job to their horn?

    Your "Free" valve job could cost you the whole horn if they screw it up and ruin the valves.
     
  3. veery715

    veery715 Utimate User

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    Ithaca NY
    Lapping is a LAST resort.

    First a good, thorough cleaning. Soak the valve pistons in a 1/2 water 1/2 vinegar solution. Wash the rest of the horn very well, using lots of soap and a good non-metalic brush on the cylinder insides. Try as best you can to clean the passages between the cylinders. Dry the bearing surfaces (piston outsides/cylinder insides) and then lubricate with a good oil.

    The try it again. If still issues, try another cleaning and a different oil. I wouldn't have valves lapped w/o trying both thick and thin oils first.
     
  4. rowuk

    rowuk Moderator Staff Member

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    If the valves stick, there is a reason. I wipe the valves dry and then "paint" them with magic marker. After playing a couple of bars, I remove the valve and see what the problem is.

    I have never had valves lapped - ever!
     
  5. trumpetsplus

    trumpetsplus Fortissimo User

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    Listen to Veery and Rowuk. Lapping removes metal. It is an absolute last resort. If you have sticking valves it is due to dirt, damage or distortion. Check for these. Are there any tell-tale scratches or dents on the outside of the casings? These can make bumps on the inside of the casing and hang up the valve. Do the valves work better when the slides are removed? If they do, the slide tubes might be out of alignment, putting stress on and distorting the valve casing.

    In other works, locate the actual problem and fix that. Don't just address the symptom.
     
  6. alant

    alant Pianissimo User

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    Aug 18, 2009
    Rochdale UK
    Rowuk
    Many thanks for your replies you have constantly heped me with this issue, just another angle on it, i have a strad trumpet same bore, when i put the valve into the trumpet it sticks slightly, however when i put the trumpet valve into the cornet it does not stick, any coments please? I fly to he sunshine today for ten days i am taking my cornet with me so i will clean clean clean and keep cleaning.
     
  7. trumpetsplus

    trumpetsplus Fortissimo User

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    From this, it appears that the main offender is the cornet valve. It is probably either dirty from a chemical buildup, has a razor sharp valve port, or is bent. Lapping will not necessarily repair any of these issues.

    Suggest the following to your tech:
    Chemical clean to remove buildup. De-bur the valve port to remove sharp edges. Straighten the valve.
     
  8. trumpetsplus

    trumpetsplus Fortissimo User

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    Sorry, I forgot one of the other main culprits. Do your horns have brass valve guides? If so, then the slot in the spring box might be razor sharp (polish this edge off), and the guides might need to be deburred.
     
  9. Masterwannabe

    Masterwannabe Mezzo Piano User

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    Sep 11, 2009
    Colorado
    +1

    I also second the comments of Trumpetsplus. One little trick I have tried and it worked for me (certainly would not work in all situations) is to place a real thin coat of Brasso on the valve, insert in horn and twist the valve in the cylinder a few times. This could have the same effect as lapping but not so severely as this too would be removing metal but very minimally. I have never seen the lapping process so I really do not know how it works but if it is anything like I imagine I would think it a rather severe process. I have actually re-plated some valves myself and so far have not had the need to lap them. Since I am not in the business of rebuilding valves I can take my time and do not plate on such a thick layer of nickel that I have to then remove any. Any touch up I do I do with the Brasso. Seems to have worked for me.

    Ray Z
    ________________________________________________
    If you don't know where you are going it doesn't matter how you get there.
     
  10. veery715

    veery715 Utimate User

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    Try swapping cornet pistons on just the cornet - put 1 into 2, 2 into 3, 3 into 1. It won't play this way, but if the sticking psiton sticks in the new location that tells you the piston is where to look for issues, and if the problem stays in the same location then it is the cylinder you need to examine.

    Follow Ivan's instructions if it is the piston, if it is the cylinder a visit to a tech is a good idea (and it is a good idea anyway).

    Well lubed and played a bunch it may improve.
     

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