Unbelievably basic question

John Schutkeker wrote:


Takes time to skill up.
Likely lack of flux or it burnt off before. Also, the metal might not have heated high enough.
Think of a plummer sweating a joint - Torch is on the work to heat. Touch solder to joint and if it melts add just a little to fill the joint. If not hot enough, then continue adding heat and re-touching.
Martin
--
Martin Eastburn
@ home at Lion's Lair with our computer lionslair at consolidated dot net
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I just recently did some silver soldering of stainless steel fittings to a pan stamped out of 16 gauge 304 stainless steel. I used Harris Safety-Silv 45 silver brazing alloy. See their website for details: http://www.jwharris.com/jwprod/hisilverbrazealloys /. The reason why they call it Safety Silv is that it is cadmium free. Older silver solders contained cadmium, a toxic heavy metal like lead and mercury. I agree with Martin, it takes practice. The silver solder melts at 1300 degrees, so you really need to get the steel you are brazing a blood to cherry red hot. Without flux the silver solder wets very poorly. But with flux it wets like crazy to a wide variety of metals, making it very useful to join dissimilar metals. I used the black stainless steel flux made by Harris. Its a brown to black water based flux that you paint on well cleaned surfaces. At first the torch dries it out, then as the metal heats up, it melts. That is your first indication that you are getting hot enough to melt the silver solder. The problem is that the flux easily burns away if you overheat the metal. But if you control the heat, and get the metal hot enough the silver solder coats everything like crazy, its hard to stop it from flowing into crevices. Beware of the fumes from molten flux, they contain hydrogen fluoride gas. The cast iron table I was soldering on was corroded by the fumes. Another problem with silver soldering steel, and especially stainless steel is that you have to heat the metal above the transformation temperature. Now I only have a limited understanding of things like austenite and martensite, but basically if you heat steel above a certain temperature, you can dramatically change its hardness, toughness and other properties once it cools, often for the worse. With my stainless I found some corrosion around the soldered joints, and I am worried that chromium carbide crystals formed in the metal from heating it too long. Still, the joints are very strong.
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A spot welder is perfect for what you are trying to do. Do some googling on this newsgroup and I think you will find information on how to make a spot welder using power transformers from Microwave Ovens.
I have kludged up a spot welder and used it to weld a couple of 3/8 ths bolts in an + configuration.
But silver soldering is likely to be the quickest solution.
Dan
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snipped-for-privacy@krl.org wrote in

This is what I thought. What do you use for electrodes? if I took it to a welding shop, what would I expect to pay, and could they get me the precision tolerance I need for precise locksmithing.

3/8ths is a lot bigger than what I'm using. Would you verify that it can weld the fine gauge wire I need?
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For 1.25 mm wire you would use a shorter time. If you are going to be doing a lot of spot welding, I would buy tips from W.W. Grainger. But for a few thousand welds you can use ordinary copper. You may have to dress the copper with a file a few times.
For better looking joints using silver solder, use less solder. It helps to use flux in addition to any flux on the silver solder. Silver soldering takes a little practice to know how hot to get the metal before adding the solder.
Dan
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