Posted by Chuck(G) on January 01, 2003 at 12:26:24:
In Reply to: valve set surgery posted by Dave on January 01, 2003 at 02:59:13:
If you need to separate individual valves, you're best off sawing them apart (use a jeweler's frame saw). Knuckles and braces are silver-brazed (temp used is over 840F, so calling it "soldering" isn't accurate) at the factory, then the valves are honed and lapped to fit.
If you try to haul out your oxy-acetylene torch and sweat the valves apart, you'll end up burning off the silverplate and probably deforming the casings by the time you've gotten them hot enough to separate.
You can use soft solder to join the valves (use a couple of short braces and a short sleeve) or you can silver-braze with a low temp (1200F) 56 percent silver brazing alloy that will be a very good match in color to silverplate. You can use MAPP gas for heat, which is probably safer than oxy-acetylene (lower heat). Brazing will always be stronger than soft-soldering, but you run the risk of deforming things by using too much heat.
If appearance is really important, then you may want to have the whole valve set replated before you reassemble everything. You might even be able to find a local outfit to do the plating for you, since you're dealing with a relatively small object (not a complete horn). Spot-plating won't have much durability, since the amount of metal that's deposited is very small.