I use the MAP Pro gas that Howard mentioned. Available from Home Depot, Lowe's, etc. most of the time. Some have it on the shelf, some do not. Price varies but usually around $12-$15. Look for a yellow cylinder.
One thing I discovered is that you can get things a bit too hot. If too hot, the braze will not flow well, if at all.
Propane might work as well but I heard it does not get as hot as the MAP Pro. The difference might not be enough to matter but I am staying with what works. Maybe I experiment with propane later.
If anyone thinks this is beyond their capabilities you should reconsider. I was wary of making such a critical part but after trying it out it is not at all difficult. The advantage of making your own horns is that you can tailor the geometry to what you need. And, one day, you might not be able to find someone to make them for you.
Well, you want the heat source to be too hot, so you can get the point of the joint to temp faster to apply the soldering/brazing material. The worst thing on a lot of work is a too cold heat source because the parent material involved is sucking away the heat and before long everything is hot except for where you want it. Get in, get it hot and get out. You learn to "control" the heat with torch setting and distance from the piece and by what you see. The big part of the flame is not the hottest part, but plays a part in keeping atmosphere off the joint to keep it from oxidizing. If you have the correct equipment and a good idea of what is going on, the way Brett describe the joint prep and the little ring of solder/brazing material is as close as you can get to be "automatic", but still takes some understanding of what's going on and using the torch correctly and that takes some practice. If you work in industry, have been around stuff like this your whole life and have some good exposure to it, plus some practical experience, it helps a lot. Some people just haven't even had the exposure. After trying to teach this stuff to people, you can see what the differences are in them. To teach some one proper torch technique, I tell them you have to be able to use your hands in conjunction with your eyes without looking at them. That makes no sense to a high percentage of people. A simple test is to see if some one can tie their shoe without looking at them. I actually used that as a practice lesson on beginners. You would be surprised at how many people can't do it.
Way back in the dark ages when I went to welding school, MAPP gas was hardly available in my area. It may have been 30 years or so before I ever saw a cylinder of it. It is a manufactured gas, and like I said , I was taught that it was dirty in nature and not as hot as acetylene but more stable. No place I ever worked had it on hand and most weld shops didn't carry it. Why it's not made any more I have no idea. I would like to play with this new stuff some time. Lots of things have changed since I was in school. I know what I learned about TIG welding basics in school as far as tungsten usage for what metal and other fundamentals. In my job search over the last 6 or 7 years I had to take an occasional welding test, and that was my first exposure to some of these changes! Certain things are just not done the way I was taught any more. When I bought my TIG welder a couple of years ago, I asked for certain types of tungsten electrodes and found that they aren't available any more! Something new was developed to take their place and no one sent me the memo! And it has a name that sounds like it came out of a comic book.!! The new machines are incredible, and the one I bought was near the higher end of things, capable of up to 200 amps of capacity, but still only needs a 20 amp , 110VAC primary supply! And it only weighs about 60 pounds. When I first bought a house, and was thinking of getting my own machine then, something similar would have cost me $10,000 or so plus a three phase line service run to my house or a phase converter. Not in the budget at that time. As soon as I get squared away in my retirement I may take some courses in the new methods and materials just so I can take better advantage my machine.
When I break something I weld it back together without even thinking about it, its so second nature. Sometimes I kind of take that for granted a bit, and wonder why some one threw something away because it was so easy to fix. Same way with fabricating parts. If I need it I make it. I agree, that if someone has any doubts about doing the work, they should reconsider it just from the stand point of expense sometimes and for safety and just buy the parts they need. But some stuff is pretty basic, and can be done with good instruction and proper procedures are followed and not a lot of expense involved.
Type at you later,
Dan McEntee