Valve Lapping

Discussion in 'Trumpet Repair and Modification' started by roltrumpet, Nov 16, 2009.

  1. johnande

    johnande Pianissimo User

    148
    42
    Jun 3, 2009
    western Wyoming
    At the risk of reviving the controversy of "home lapping" and at odds with the apparent concensus above, I would offer the following: My vintage (?) Kanstul made French Besson developed a very slight "drag" in one valve, noticeable only occasionally and primarily during fast passages. I cleaned the horn (spotless), checked for any unusual wear patterns on the valve or casing, tried thinner and thicker oils to no avail. I called my local technician and asked his opinion of "home lapping" using purchased lapping compound and following the procedure recommended by the manufacturer. His suggestion was "don't pay for lapping compound -- use lava soap." I said thanks and immediately called a tech for a nationally known music store who has done some work for me previously. He listened to my story and said he agreed with my local tech. I tried it; problem solved... at least for the time being... lol, huh????? JA
     
  2. veery715

    veery715 Utimate User

    5,010
    1,802
    Mar 6, 2007
    Ithaca NY
    So you got your hands clean. Now what about your trumpet?
     
  3. johnande

    johnande Pianissimo User

    148
    42
    Jun 3, 2009
    western Wyoming
    Veery715... You surely don't think I would put that stuff on my horn, do you???? JA
     
  4. ComeBackKid

    ComeBackKid Fortissimo User

    2,858
    68
    May 11, 2009
    Yorba Linda, CA
    There are several recent threads related to this - but to save the search, I will repeat my post here. I asked a highly-experienced and skilled tech this question. He said that in the absence of the PROPER lapping compound (that depends on the situation), a safe method is to use toothpaste. He recommended Pepsodent as the one having the best characteristics. I found some at a 99cent store and it seems to work well. It may take several applications to clean the gunk from the inside of the casings which is where most of the problems appear to be. Just wet the piston, smear a bit of toothpaste on it, insert by hand into the casing and move it up and down for awhile. Repeat as necessary. The toothpaste washes out easily when the lapping is done. It can also be used to clean your mouth before playing which may help keep the gunk from building up again.
     
  5. rowuk

    rowuk Moderator Staff Member

    Age:
    61
    16,611
    7,954
    Jun 18, 2006
    Germany
    Brush your valves three times daily...........

    The problem with a thread like this is that you can give an answer for a tech that has no supplies (toothpaste) and have no fears that the horn will be fine afterwards. You can also answer the kiddies (Don't try at all!) and of course cover all of the other types of people that you can think of.

    The bottom line is that there is ALWAYS a reason that a valve sticks, and that is NEVER because it wasn't lapped properly at the factory. IF the horn is not properly cleaned BEFORE messing with the valve, the gunk from the lapping process will just add metal particles to the garbage already in the horn.

    The second issue is that removing material can make the valve WORSE if it is already considerably worn.

    The first step is to locate the real problem: dirt in the horn, scale build up, mechanical issues like worn springs/valve guides or dents. Once all of that can be ruled out, there could be a small chance that careful lapping could remove the problem. Lapping is not the cure for sloppy action or sticky valves. The cure is to identify the real problem and address that.
     
  6. Kang-Ling

    Kang-Ling Mezzo Piano User

    516
    74
    Oct 8, 2009
    Frigiliana
    ...so, the perfect trumpet has perfectly lapped valves, 100 % airtight ( cero air-leak )??
    I suppose theire is some tolerance ?? because
    "completely tight" means no space for any oil...
    (so what helps to avoid "escaping" the air is the oil ??)


    thin oil for the more "perfect" valves and the thick stuff for the others ?¿?

    what´s the sound-result of leaky valves ??
     
    Last edited: Dec 15, 2010
  7. gzent

    gzent Fortissimo User

    3,724
    758
    Nov 5, 2003
    Rochester, MN
    I've lapped valves on my own horns and horns I customized for paying customers, but
    only after being taught in person by a NAPBIRT approved brass tech what the whole process is about. Which I will not describe because if you haven't been taught in person you will likely ruin your piston, valve block or both.

    TAKE IT TO SOMEONE WHO IS A PROFESSIONAL!
     
  8. gzent

    gzent Fortissimo User

    3,724
    758
    Nov 5, 2003
    Rochester, MN
    Absolutely!

    I'd guess most of the time its due to grime and/or lack of oil, following by worn plating, then a cylinder out of true and lastly a (lightly) scratched piston, which is really the only (normal) thing I would address with lapping.

    A chipped (cracked plating) piston can't be fixed with lapping. It might stop sticking for a few days until the super slick surface "wears in" again, but then it will start sticking again, and will probably be worse because you've removed even more of the plating. So, lapping is only advisable for light scratches or perhaps in a case where the valve block has been heated up quite a bit during a repair or rebuild.

    If the valve block approaches the heat needed to melt solder then you can see some copper "liberated" from the cylinder walls and a VERY light lapping might be needed to remove the free copper and set up the hard, metal worked brass surface of the cylinder again.

    Again, there are steps for skilled repairmen with a lot of patience and experience, not someone wanting to "fix" their own horn
    based on something they read on the internet.
     
    Last edited: Dec 15, 2010
  9. Silversorcerer

    Silversorcerer Forte User

    1,323
    306
    Jun 9, 2010
    Atlanta
    I found that most of my valves that stick will stick in the bottom position, and all of my horns are vintage horns that have been dormant for a while before I bought them and started playing them again. Cleaning and frequent playing does wonders for theses in most cases, but in some instances there is some corrosion that generates friction in the open area at the bottom of the valve casing. Those deposits will cause the valve to stick down. The corrosion can even make something like a bathtub ring at the bottom of the valve edge that will hang up a valve and keep it from returning. Note that this is not a result of either valve wear, poor lapping at the factory or damage to the valve casing;- it is a result of there being sufficient oxygen in the bottom air space to support more corrosion than in the casing tube in general. It can be present in a worn valve casing or in one where the valve looks pristine and new.

    Something else some might have noticed: On some older horns, the valves and the casings are not perfectly cylindrical, and perhaps never were. If you rotate a valve 180 in it's casing it will probably not only not play, but it might not move up and down fast or it might not move at all. I have two different vintage mellophones whose lapping job is such that the valves only travel well in the tubes when these are in the proper orientation, so the valve cylinder has been lapped to whatever the shape of the tube interior is and neither are perfectly cylindrical.

    I see little harm in removing that corrosion in the bottom of the casing tube at home by hand with a good fine polishing compound. My method was to use Happich semi-chrome polish on the tip of my finger and just finger rub the inside of the casing at the bottom until it feels continuously smooth in that lower area. Happich probably contains either pumice or rottenstone or something similar, as well as some light weight corrosion dissolving chemistry. Most of the material you remove is corrosion or dirt deposits and you are only removing it at the bottom of the tube. Another area where deposits seem to build up is on the very edge or corner of the valve cylinder at the top or bottom. Again, this is mostly a symptom of a horn sitting unused for several years. If you can feel a roughness around the edges the cylinder, these can be dressed smooth by hand with jeweler's rouge on a leather surfaced pad and very careful light polishing. You never want to use a polishing compound that leaves abrasion lines. You want a polish that leaves a glassy smoothness with no visible abrasion at all.

    I think it bears mentioning that unless you are familiar with maintaining machines, motors, engines, and other mechanical devices, you want to consult a professional or have a pro do all the work. I have a couple of horns that look like someone used fine grit sandpaper on the valves, and of course that pretty much sets those horns up for needing re-plating or more serious maintenance.

    The safest advice is to always have experienced pros do the work. It is far easier to ruin something than fix it. I do recognize that as concerns mechanical things, some of us have far more experience dealing with these than others and will venture to try something at home. Well, just don't use any power tools and remember;- it's not woodworking and glue ain't gonna fix a mistake. And as has been pointed out earlier, proper diagnosis is paramount. You don't want to be polishing away any metal when what is really needed is a thorough cleaning. Dirty scale on the inside of a tube can blow into a valve and cause it to stick immediately.
     
    Last edited: Dec 15, 2010
  10. Ralph

    Ralph Pianissimo User

    50
    1
    Jan 27, 2005
    At the risk of seeming like I'm endorcing lapping your own valves, here's a great site for all sorts of repair projects.

    MusicMedic.com: Triumph Lapping Compound

    I have lapped 1st and 3rd slides, but would never lap the valves.
     

Share This Page