I am silver soldering brass and carbon steel in making clock parts using a high temp solder and a MAPP gas torch. What might you recommend to minimize the amount of cleanup needed, thermal paste? Is so what's good etc, or are there other means. My end results are polished parts and what ever can be done to make it easier is what I am after.
Thanks,
Rog
What might you recommend to minimize the amount of cleanup needed
What might you recommend to minimize the amount of cleanup needed
What might you recommend to minimize the amount of cleanup needed
It helps to use lots of flux. Flux loaded with oxides is much harder to remove, so a surplus of flux actually makes cleanup easier. Hot water usually is sufficient.
Cleanup of *what*?
If you are getting a lot of oxides on the parts, you need to use more flux and a softer flame so the flux does not blow off and leave exposed spots.
If you are worried about the flux itself, soak the parts in boiling water to remove that.
If you have trouble with the solder running where you don't want it, that can be remidied with "stop-off" which is a paste or paint sold expressly for the purpose of preventing silver solder or braze from adhereing where it isn't wanted.
Jim
Milk of magnesia. Paint the areas to be stopped off with it.It repels the solder. We use it at work when furnace brazing all the time, and jewellers use it as well.
Why are you silver soldering clock parts? (Non adjustable assemblies are drive fitted or riveted; even soft solder is only used on cheaper French clocks. I have never seen silver soldered parts unless used to repair a broken original part.). Silver solder heat (1100 degrees min) takes the hardness out of the brass and steel which cannot be then be rehardened without the solder joint moving. And since brass must be work hardened, you cannot reharden it without changing the shape/dimensions anyway. Over time soft brass gets charged with abrasives and acts as a lap, the soft steel wears and will not yield a high polish.
As for the soldering, you may be using too much heat, your soldering block may be contaminated, or you may not have adequately cleaned your parts. If you have everything cleaned, you should need very little flux at the joint and even less solder. There should be no need for thermal paste or antiflux.
When I silver solder I use a very small flame from a jeweler's torch and "sneak up" on heating up the parts. The instant the solder flows I back off. I use propane/oxygen which I believe produces a cooler flame then Mapp. I have used this torch to fuse brass to steel in making a balance wheel so I know it is more than adequate heat for any job in clockmaking. I wonder if the Mapp torch is simply too much?
What kind of filler metal are you using? All silver brazing rod is not the same - with higher silver content (say, 50%) you will get better fluidity than low silver content rod. Dave
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