Re: Re: valve set surgery


[ Follow Ups ] [ Post Followup ] [ TubeNet BBS ] [ FAQ ]

Posted by Dave on January 03, 2003 at 01:24:06:

In Reply to: Re: valve set surgery posted by Chuck(G) on January 01, 2003 at 12:26:24:

Chuck, thanks for the info. I posted a reply, but I guess the ether got it, so here is
a second try.

Is there a way to avoid the problem of burning the silver? Silver melts at a substantially higher temp. than silver solder (1700 deg. F vs. 1200), so my plan
is to use liberal flux to prevent oxidation during de-soldering and re-soldering.

I do use oxy-acetylene. I have a small Victor torch, use a 00 tip size and use it for everything incl. solder and silver-solder. It does a much nicer job than propane, much better control of heat, much less discoloration and much more localized heating. I have not tried Mapp gas, but I have seen no side-effects with oxy-acetylene, so I wonder why
a lower heat flame would be an advantage... With oxy-acetylene, if you use thin silver-solder wire, or cut small pieces and place them around the joint after fluxing, you can heat the joint quickly enough that the soldering is complete before any adjoining soldered
parts are even warm. Just about the same time that you see the solder wet the base metal the job is done. A good wrist-motion to heat the joint uniformly and avoid overheating takes some time to learn, but it is not a skill unique to musical instrument
repair...

I expect that distortion will not be a problem due to removing the casing, rather it would
be due to differential expansion at the time the casing is being re-soldered into the new
cluster, which gets locked in as the cluster cools. The best solution is to preheat all
parts to a substantial temperature and control the rate of cooling. However, I am hoping
that if I make a jig to hold the parts in alignment, and if I do each joint one at a time
and cool in between, the oxy-acetylene torch will localize the heat enough that
distortion is avoided. I'll let you know how it turns out.

My fallback plan is to get the cluster replated and have the valves rebuilt if the problems occur. I'm planning on taking pictures of the project as I go. The end result
will be a five-valve double bell horn.


Follow Ups: