Learning to Silver Solder

I got it to flow!

My first successful effort. not neat, but it worked. This piece is just the brass pipe sitting on the brass strap.

So, before I can make my new exhaust header, I need to learn how to join the pipe, and the piece of metal.

I thought I would investigate brazing the pieces together, as it seems like the best way to join the two relatively small and thin pieces together.

Upon doing some reading online, there appeared to be 2 categories, Silver Soldering, and Brazing. Both seemed to be a very similar process, but there seems to be some difference between silver soldering and brazing, and my understanding those are:

  • Silver Soldering uses filler rods which contain, as the name suggests, Silver, whereas actual brazing uses bronze filler rods.
  • Brazing requires more heat, due to the bronze filler rods having a higher melting point, and as thus, you really want oxy/acetylene gas.
  • Silver Soldering isn’t very good at filling gaps, close fit up is needed. Brazing is much better at filling gaps in a workpiece.

Now, that may, or may not be completely accurate, but that’s my current understanding of the differences. I’m always willing to learn more if you are knowledgable of the matters.

the 2% sliver rods are what i'm using

These are the silver solder rods that I'm using. 2% seem to work. Higher silver content makes them melt at lower temperatures.

So, off to Bunnings to take a look at what they have. They are selling flux coated brazing rods suitable for what I want to do for $14 for a pack of 4 maybe 6, or much longer lengths (about a meter i think) of 2% silver rods for about $2 a length. Then, of course you have to add flux to the cost of the unfluxed rods, which adds about $15, but a small container of flux will last a long time, and is a lot cheaper if you are using more than a few lengths. I went with the 2% rods, and a container of flux.

Ezi-Weld flux

Ezi-Weld flux 602 silver soldering flux. You need to make sure you get Silver Solder flux, not soft solder flux, otherwise it won't work.

My first attempt didn’t go very well, I couldn’t really get the brazing rod to flow, But the next day I tried again, and things seemed to work much better.

I put my initial problem down to not enough heat. My first go I was trying to heat the brass on a 3/4 of paver brick, which I guess I needed to heat up too, before it would stop stealing heat from the brass. I also worked out there is a sweet spot in the gas torch where the most heat is generated. The first day I was playing around trying to work out that position.

My second go was done mostly on the other  1/4 of the paver, which seemed to heat up quicker. I’d learnt from the day before on where to hold the flame, and everything was great.

The second successful attempt, with the pipe mounted in a hold drilled in the plate.

After having some initial success, I decided to take it one step closer to the likely final product (the exhaust pipe for my nitro car).  I drilled a hole the same size as the pipe in the piece of brass, and inserted it to make sure it fit.

Cleaning up the pieces with a wire brush, i then fluxed both pieces, before refitting them together, and resting the workpiece on my paver brick.

Bottom of the thru hole

This is the bottom side of the thru hole joint. All of the solder was applied to the top, and was sucked thru to this side

I fired up the gas torch, with my new flint lighter, which is so much easier, as well as safer, then using matches. I’m so glad I picked up one of these bad boys. The silver solder flowed nicely and made its way right thru to the other side, as you can see from the picture above.

Flint lighter

I always thought these were just for oxy/acetylene torches, but they work perfectly for LPG too!

So, that’s the state of my silver soldering. Next will be having a go at trying to get the tight bends needed in the pipe. I’m still trying to decide if I want to do this in brass, or have a go at the aluminium, or just plain steel. Before I make that decision, I’ll have to do some weighing up, mostly of being able to get the right sized metal.

Anyway, that’s all from me for this week. Stay tuned till next week, when I find something else to talk about.

The gallery:


2 thoughts on “Learning to Silver Solder

  1. I am very happy to have come across this info. I don’t have any experience of welding, brazing or silver soldering, but I was thinking last week of using silver soldering for making connections to the terminals of stove plates of my not-new stove (as part of re-wiring the stove). I called around at an Afrox (African Oxygen) outlet in Johannesburg, South Africa on Friday last week, hoping to find a kit for DIY use (i.e. reasonably priced) for myself to use, but the prices were prohibitive for my needs. This is why the article gives me hope that one can use LPG gas for silver soldering. Thank you!

  2. Thank you for your information very helpful.

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