Piston Valve Construction


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Posted by Jay Bertolet on February 22, 2004 at 20:14:33:

I have a question for those on the board with some expertise in how tuba piston valves are made. Let me give you the background:

I found a wonderful repairman this past weekend in neighboring Fort Myers, Florida. This guy runs a small music shop called First Note Music and, in addition to selling a limited number of instruments and running a private lesson studio, the owner is a pretty good instrument technician. One of my horns, a Nirschl 6/4 CC, needed a cleaning in the worst way. What intrigued me about this particular shop is that the cleaning service they offer involves a sonic cleaning. The owner explained to me that the manufacturer sells two sizes of tanks and the one he owns is the smaller of the two. Not large enough to completely immerse the horn but large enough to rotate the horn and clean it in sections.

After getting the horn back, I was thoroughly amazed. The valves and slides were cleaner than I have ever seen them. It was really a remarkable difference. But something unusual happened. There appeared to be some flaking of plating inside the piston casing of a couple of the valves. The technician was surprised by this because his training indicated that such plating shouldn't exist. He thought that piston casings would be machined brass and that the pistons would be heavily plated so that they could be fitted to the casing. Plating the inside of the casing makes no sense in this case, at least so he thought. But clearly you can see a small section in two of the casings where the metal is a different color than the majority of the casing interior. It almost looks white, like maybe the casing is made of solid silver and then plated with brass. This makes no sense because the tech didn't think that brass would even plate. He was unsure if this apparent flaking presented a long term problem or not. The tech couldn't feel any edge to this area and he polished it but couldn't get more flaking to occur.

Does this sound familiar to anyone? Is it possible that the insides of the valve casings are plated? Has anyone ever heard of anything like this? Is there a fix other than removing the valve section and doing a complete valve job? The tech was unsure as to whether this flaking would continue or even if it was some weird sort of reaction to the sonic cleaning. Any ideas would be greatly appreciated.


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