Metallizing

[twoconnguy]

I did a search and nothing came up so here goes. Has anyone ever heard of using metallizing or thermal spray to rebuild valve sets? Thermal spray is a generic term for a group of commonly used processes for depositing metallic and nonmetallic coatings. These processes are flame spray, plasma-arc spray, and electric-arc spray. Coatings can be sprayed from rod or wire stock, or from powdered material, and a wide variety of alloys and materials can be applied, depending on the need for wear or corrosion resistance. Typically the built up surface is cylindrically ground to the finish size after spraying. I understand the need for art and hand crafting in creating a tuba that sounds good, but as an old machinist who morphed into a manufacturing engineer, I am always surprised at how little of modern manufacturing or remanufacturing technique is applied to the valves. I'm constantly in awe of the work that Mr. Oberloh does, but it seems, from an engineering viewpoint, more labor intensive than it needs to be when it comes to the valves. I've always sensed a certain Luddite attitude in the musical community, but hey, progress gave us valves didn't it...or taken to the extreme, we'd still be the didgeridoo section. Any thoughts from Mr. Denney or Mr. Schultz, or others with industry and tuba experience?

[Chuck(G)]

I've long maintained (if you've read this board for very long) that TiN PVD would be the cat's meow for mouthpieces. Totally inert, very hard with a look like gold (just like those "gold" bathroom fixtures).

While it might work on pistons, the problem is the same with mouthpieces--you need to do a large batch of things to be economical.

And that seems to be the rub with most musical-instrument related processes. There's no good reason that trumpet bells couldn't be spun on the same automated equipment that makes stainless-steel bowls, woks and vases--basically you feed a pile of metal discs in on one side and spun items come out the other.

But who has a use for five or ten thousand trumpet bells per day?

[iiipopes]

Don't laugh - if China really gears up for a world market, they could make that many.

I believe valves could be made superlative with teflon impregnated modern ceramics. Then any liquid, including plain water, could be used as the emphasis would be on sealing the ports and not necessarily lubrication to prevent wear.

[Dan Schultz]

Has anyone ever heard of using metallizing or thermal spray to rebuild valve sets?

I'm familiar with using the technology you mentioned to build up machinery shafts and I suppose it could be used to rebuild horn pistons... but... what could be easier than heavy copper plating, cylindrical honing, nickel plating, and a bit of hand lapping? It really doesn't get any easier than that... and it doesn't require major investments into technology.

After having spent over 30 years in automation and manufacturing design engineering, I am amazed at some of the 'old World' ways of doing things that are still in common practice. I think Chuck pretty well summed it up when he stated that the World wouldn't know what to do with millions of trumpet bells.

[Rick Denney]

Thermal spray is a generic term for a group of commonly used processes for depositing metallic and nonmetallic coatings. These processes are flame spray, plasma-arc spray, and electric-arc spray.

While it's the preferred method for building up the bearing surfaces on the cast iron steering knuckles on my motorhome, wouldn't the heat of these processes cause the brazed or soldered joints to come apart?

Rick "thinking a 5300-degree arc is hotter than the 1600-degree melting point of silver brazing material" Denney

[Chuck(G)]

Rick "thinking a 5300-degree arc is hotter than the 1600-degree melting point of silver brazing material" Denney

Depends on the process, Rick. One can coat plastics such as ABS using low-temp PVD. Here's an outfit that offers such a process:

http://www.richterprecision.com/PVD_coatings.htm