I find silver solder flux doesn't flow well so coating all areas before assembly to which you intend solder to stick is helpful. You also need some space in the joints for the solder to flow into, maybe 0.005 thou. Basically, make your fits pretty loose.
Silver soldering 12L14 Steel
- Thread starter Harold Lee
- Start date
Help Support Home Model Engine Machinist Forum:
jpeter said:
I smear the flux on anything I expect to get braze, even if I think the flux will be removed when assembling. The are different "thicknesses" of silver solder - thin (easy flow) and gap fill (thick), the gaps needed for the thin stuff are a lot less. When you have a gap you can make it stay in assembly using a center punch to upset material - if used on a rod end in a hole it's maintain the gap you need all around while keeping it centered. I like to use one of the automatic center punches for that, keeps the punch size (and thus the upset height) even.
Good tips. I generally fixture the parts but seems the center punch idea has a lot of merit. I'm going to try it.rkepler said:
There's a lot to be said for using the right amount of heat too. Get silver solder too hot and it kinda ruins it. Not hot enough and it won't flow at all. With lots of flux on it and the heat just right its amazing stuff. Hard too to get something as large as a crank hot enough with a propane torch.
jpeter said:
There are propane torches and then there are propane torches:
The bigger one throws a flame about 3 feet and is good to about 4-5 inche diameter copper tube. The smaller one I use more and is good for most things I do. The torch handle connects to a 20# propane tank, the big tip will cause the tank to cool noticeably.
You can get those giant propane torches as "weed burners" from Harbor Freight and similar. They are cheap. And LOUD. At full throttle, it's like a jet engine. Gobs of BTU's.
How about $19 for USA people?
Creating a "hearth" for such a process can be challenging. Firebrick works well. But one of the problems you get when using a giant torch in a hearth is that it's so big, the entire work area is enveloped in blue flame, it's hard to move, and it's hard to dab the solder into the gaps where you need it. That's why I prefer a hotter, hand-held torch that does more of a localized spot-heating. That's the thing with silver braze, you know when the temperature and flux is right... it flows beautifully. It's amazing when you see an internal braze fillet that has flowed into a 0.001" gap for several inches. You know that bond will NOT fail.
Nice tip with the center pop. Knurling will also do this. I think it is also wise to turn a groove in the tube's OD where the solder will go, and/or chamfer or bevel the ID of a tube, when brazing a solid or tube into another tube.
How about $19 for USA people?
Creating a "hearth" for such a process can be challenging. Firebrick works well. But one of the problems you get when using a giant torch in a hearth is that it's so big, the entire work area is enveloped in blue flame, it's hard to move, and it's hard to dab the solder into the gaps where you need it. That's why I prefer a hotter, hand-held torch that does more of a localized spot-heating. That's the thing with silver braze, you know when the temperature and flux is right... it flows beautifully. It's amazing when you see an internal braze fillet that has flowed into a 0.001" gap for several inches. You know that bond will NOT fail.
Nice tip with the center pop. Knurling will also do this. I think it is also wise to turn a groove in the tube's OD where the solder will go, and/or chamfer or bevel the ID of a tube, when brazing a solid or tube into another tube.
Similar threads
