A little more on Silver Soldering

[3-in-1]

My currently most used setup is with the trigger igniting torch with Mapp tank sold at Lowes or Home Depot. i think it was about $40-50. A single soft fire brick from a brick and concrete company which was not cheap but only needed one. Silver solder and flux from a plumbing supply house which was about $25 when i got them a while back. So for under $100 you can have everything you need to start. I have used oxy-acetylene but for most jobs the little torch works just fine. Get the hottest version. For doing little jobs the single brick works pretty well. Surprisingly you can solder stainless and brass by this method. One correction to the very informative posting on silver soldering is about welding. In welding the parent metals (those being welded) reach their melting points but in silver soldering the parent metals only have to reach the melting point of the silver solder. This is why you can't silver solder low melting point die cast, zamak pot metal with 1300 deg F silver solder. Do not confuse this type of solder with that sold at hardware stores that might be marked as silver bearing solder which is a much lower melting temp solder. One other tip I can think of is to run HOT water over the part to loosen the baked on flux which is now like glass and hard to wire brush off. As an example of what can be done with silver solder is making longer key blanks from two shorter ones, a 6 or 7 pin from two 5 pin blanks. Been doing that for 35 years now. Doug

[gloves]

Thanks for sharing your experience and tips

What did use your oxyacetylene torch for? Whenever I used one, I found it was too powerful and hot for any small work, same with electric arc solder
On the other hand, I had very good feedback with propane-mixes handheld torches, which are something closer to what you've described.

Fire bricks are expensive and AFAIK the best ones are made out of alumina, which is outstanding yet brittle.
I don't want to go too much offtopic, but I think alumina could be bought raw then compressed into bricks, though I've never tried.

[DayZiro]

Is this a continuation of a different thread?

[3-in-1]

Gloves, you pretty much answered your question. Things that were too large to efficiently use the propane torch on. However you can use a big torch on small parts. You just have to hold it back further and become familiar with the heating rates. And to Day Ziro, yes as of right now it is related to the thread immediately above this one.

[DayZiro]

Ah, it seems so obvious now.

[3-in-1]

The ideal gap between the parts you want to solder is .001" - .002". And when done properly can be amazingly strong. One of the keys I lengthened has been on my keychain for about 20 years, is quite worn and has never broken.

[3-in-1]

One of the most difficult things in silver soldering is the jigging or fixturing of the parts. There are jewelers tools available with little spring clamps on movable arms that come in handy. But most of my work is just laid out on the brick using whatever is at hand to hold the parts in position. Small, easily moved parts can be a challenge when bumped by the solder wire so consider this before you put the torch to it. You can use larger heavier metal pieces to hold things in position. A related topic is when you are fixing a large piece to a small one. Since you want both to reach the solder melting point at roughly the same time and avoid overheating the small one, learn to focus the torch mostly on the larger part. Another tip that took me years to figure out was to do the machining after the parts were joined not before. An example would be restoring a worn mortise lock thumbpiece. I would square off the worn part with a grinder and file, then solder a tiny piece of brass or bronze to build up the part back to original size. Keeping the little piece in place and from overheating was always a challenge. It is usually, far easier to solder on a larger piece and then cut, file, grind to size.

[3-in-1]

A very important topic when silver soldering is the effects of high heat on whatever it is you are repairing or making. The annealing (softening) or hardening of high carb steel is a very real possibility. The topic of tempering hi carbon tool steels (includes spring steels) can get very complex and one way of easily reducing that possibility is by using a heat shield product to cover that which you don't want affected. I am not at home this week end so I can't give the brand name I use but it is pretty effective. And I am not sure whether I got it from a welders supply or someone like Brownell's Gunsmithing supplies.

[Al]

I use old bricks from a storage heater but have also used old radiants from a gas fire in the past. Radiants all broke fairly quickly though as very delicate.