Lapping Brasswind Valves
By: JL Bowers, The Bandroom

At times, a brasswind valve will get sticky, get a very small ping dent or scratch in it. You also may be one of the unfortunate souls that has to buy a new valve for your horn because it was dropped or otherwise damaged beyond repair. All of these instances can be easily corrected with the use of lapping compound.

Lapping Compound is a must have when installing a new piston, or to aid in the removal of small burrs from inside a damaged valve or rotary casing. This compound is made from an extremely fine abrasive. It will polish out the inside of the casing and smooth any high spots in valves and casings.

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Directions For Use
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Lapping Compound

Lapping compound is a syrup-like liquid, ultra-smooth compound with very fine components in it. Some refer to lap as very harsh and prefer toothpaste. However, this is even finer than that! So, you wont harm your valves using this if you follow the directions below. Lapping Compound is used commonly in brasswind repairs to free sticky valves, and smooth out small burs in the valve casing. It is also used to smooth out slides that have been damaged, and to aid in rethreading valve caps. Anywhere there is a problem with metal-to-metal contact! Lapping compound is usually an alternative for smaller shops or individuals that don't have acceess to expensive valve truing tools.

How To Lap A Valve

* Take all the valves out of their casings and remove the fingerbutton, cap, felts, corks and valve guide from the problem valve. Be sure to take note of how
to re-install all parts correctly. If you can; it may be a good idea to take a picture!

* Carefully remove all the slides from the horn. If the slides are too stuck to easily pull free by hand...

Consult a professional repair technician!

* Smear a small amount of lapping compound about the width of your fingertip all the way around the outside bottom of the problem valve. Less is better in most instances.

* Place a few drops of Super C Valve Oil on the valve and insert it into the correct casing. Align the piston as if the valve guide was still intact and work the valve slowly up and down several times, then remove the valve.

*Spray some household degreaser on the valve, inside every casing and inside every slide tube. Scrub out with a cleaning brush. Rinse well with lukewarm water.

(DO NOT USE HOT WATER!)

* Dry the instrument and valve well. Reassemble the horn and lube the valves. If it still feels sticky or rubs, repeat the process. If it is still sticking after two laps, you will most likely need to consult your local or Online Repair Shop about a professional valve repair.

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