07/08/2026
Let’s end the week with a bit of a rant…
Valve buffing revisited
Nothing demonstrates a repair techs complete lack of comprehension of how a brass musical instrument operates than to buff a piston (or rotor) to oblivion.
Here we have a Yamaha YTR-6335 trumpet. There was, at some time in the past, a dent put into the 3rd valve casing. A competent repair tech would remove the dent and then, only if absolutely needed, lap the piston into the casing for a final fitting. However, this person decided to leave the dent and just make the piston rather a bit smaller to fit past the dent. So, yes, the valve does go up and down with modest reliability but at the cost of intonation, slotting, tone and efficiency.
We use a magnehelic machine to test an instrument’s air tightness or “compression”. A quick test on one port of the undamaged 1st piston gives us an excellent reading of .1 inH2O (inches of water is basically a finer scale of kPa or psi). The damaged valve with a heavy valve oil gave us an abysmal reading of 7.2 inH2O. When you consider we’ve set this machine up to start reading at 8 inH2O it means this valve barely creates a reading at all. Put it this way, I’ve had instruments that have endured 100 years of use in a brass band that give better readings than this!
So, valve destroyed and new one on order…
