The Home Machinist!

If using something like a Victor 100 series torch, what tip size is best for silver Soldering larger parts and piping?

-jlakes85

Define 'larger'.....

I was watching Dave scalavi on YT silver solder some smokebox piping that was 1/2 copper, using a soft flame. Something around that size

you can use a propane torch for smaller (1/4" copper) to silver solder. Really need to experiment on scrap if you are just starting and get used to seeing the flux melt and know when to apply the solder. On heavy stuff I have even used my cutting torch to heat it up. You have to be careful with acetylene as it will melt your part quite quickly. So, as I said practice, practice, practice.
Fred V

As I've written elsewhere on this forum, I use an O/A torch with indirect heat on the parts to be soldered. I heat the underside, back side, or from below with the part sitting on a piece of steel, playing a long feather flame on the steel rather than the part. The size of the tip depends on the size of the part. I can't give you a recommendation because, as others have said, it takes practice. The challenge is to get the right amount of heat into the part so that the part melts the solder. You don't want to melt the solder with the torch. In such a case the parts may not be hot enough for the solder to make a good bond. But you don't want the part to get too hot, or just hot enough to melt the flux but not the solder. I just recently soldered two bits of steel to make a couple of small angle brackets about the size of the last joint on your thumb (photo below). I set the bits on a piece of angle iron held in the vise and heated through the underside of the steel angle. I used a No. 4 tip with a flame about 12 inches long, heating the angle iron from the underside until the heat soaked through the bits. I put little pieces of solder along the joint. I don't like to feed solder onto the part as I usually end up with too much solder. And by setting bits of solder on the part, you'll know when you get to the right heat as the solder will melt and suck into the joint. I also use the cadmium alloy solder as I think it flows better, and the black flux because it doesn't burn off like the white can.

When you say "larger parts," I made up some journal boxes for arch bar trucks and I used a weed burner on propane for those. The combined parts were about the size of a dinner roll; there were six separate bits to make the complete journal. I did have to play the flame directly on the parts but I set them inside a little hutch of stacked firebrick and kept the flame moving so the metal would heat and draw in the solder. It took some time for the parts to heat up and the radiant heat coming back to me was almost too much to bear. But it worked fine.

#3 or smaller tip is a good place to start, but don't go crazy since you can overheat very quickly.

Bill,

Sounds good. I picked up a #2 to go with the #0 that came with the set. I figure a soft 6 inch flame should be more than enough for an O/A only joint. I don't want to go broke constantly changing tanks on joints l that clearly require propane preheat BTW, who sells seivert in the US now?

Hi,

If you are going to use Oxy acetylene for silver soldering,you must use a slightly reducing flame and just use the wash to do your heating. Also, don't try to rush things. You must give it time to let the heat penetrate. If you watch carefully, you will see that the silver solder will follow the heat. Remember, oxy/acetylene is a MUCH hotter flame than propane/air so if you aren't careful, you can wind up with what looks like a good joint, but have no penetration.

The best combination for large items (especially with copper) is to use a large propane torch (weed burner type) to heat the part and then use just the wash from the oxy/acetylene flame to supply the extra little bit necessary to cause the solder to flow. An added benefit from this system, is that the wash from the large torch protects the metal in the immediate heated area from oxidation. If you remove the torch, you can see the heated area oxidizes immediately, but moving the torch back protects the area again. With this system, you have very good control over the process.

This is the method Don & I used for silver soldering the Big Boy boiler. Using this system, it took us a good ten minutes to get the boiler hot enough before we could even begin soldering the joints. Copper pulls the heat away VERY fast. It also helps if you enclose large parts in an "oven" made from insulating firebrick.

This is what we learned by sometimes doing things the hard way.

Richard Trounce.

you can get Sievert from Sievert...

Google and poke around. Amazon sells them as do a few other places

jlakes85, check out my Sievert torch thread:

http://www.chaski.org/homemachinist/vie ... p?t=103396

The Sievert I got was enough torch to silver solder a copper 5" barrel for a 1" scale locomotive. Understand, you need fire bricks to make a hearth to keep the heat in. Refractory firebricks, not stove firebricks. My boiler was certified in May of 2017.

David

Hi,

To clarify things a bit, there are several kinds of firebrick. All will take high temperatures, but they aren't created equal. There are at least two different grades of insulating firebrick, G20 and G23. The higher number is a better insulator but has less mechanical strength. They are very light because they are mostly air. That is also why they aren't very strong. You can put a torch on one side; the brick will become almost white hot immediately, but when you take the heat away, after a few minutes you can put your hand where the torch was.

Regular firebricks are much stronger, but they are heavy and their heat conductivity is much greater. It takes quite a while to get them red hot or hotter and they cool down quite slowly. If you are going to make a regular furnace, you face the inside with regular firebrick because of its strength and use the insulating brick to support the firebricks because of the insulating brick's high insulating ability. At Corning we had a gas fired kiln that ran all the time and it was made this way. The peak temperature in the kiln was a little over 1,100 degrees centigrade.

I have a supply of the insulating variety which I find very useful.

Richard Trounce.

The fire bricks I used to make my boiler are K-20 Insulating Firebrick. They are available off Ebay. These bricks reflect the heat back into your work. Stove bricks absorb and radiate heat. For silver soldering, the stove bricks do not work very well. The insulating firebricks work great, and, yes, they are fragile.

David