I strongly recommend the use of oxygen concentrators for brazing instead of bottled O2. Much safer, and other than the little bit of electricity they use, you have unlimited free O2 from then on. OK there is the initial cost of the concentrator (they're stupidly expensive when new, so buy used) and some maintenance costs if parts wear out — nothing on mine has yet. It cost $200 when I got it a few years ago and sometimes I see them even cheaper. They're medical devices so they tend to be well made. They're often available cheap because the patient died and the family just wants rid of it. Ignore the small/portable ones; they're expensive due to miniaturazation and ability to run off a battery, so the bigger 120V AC ones are cheaper.
Your competition, the other people likely to buy it before you get there, tends to be lampworkers or glass-blowers.
Mine puts out 5 liter per minute at somewhere upward of 90% pure O2. It keeps up with the torch tip sizes I tend to use, short of a rosebud.
10 l/min devices exist, but 5 l/min is much more common. 10 l/min ones tend to sell for lots more, like over double, so if you want to run a rosebud it's probably better to buy two 5 l/min units and run them in parallel with a Y hose adapter.
I use a standard 20 lb propane bottle, available at the grocery down the street. No more trips to the welding supply for bottled gas! And it shouldn't make your insurance company lose their excrement.
You do pretty much need propane-specific tips, because the flame detaches and blows out if you use acetylene tips. There are workarounds but the best tips I've found are from
Paige tools. They make a pointy concentrated flame not too different from an O/A torch, and they never blow out. I use them with a Smith AW1, a classic "aircraft" style welding torch, and with a Meco Midget, but Paige makes adapters for several other torch types, like Victor, Harris, and clones thereof. No affiliation, just a satisfied customer.
Where I'm comin' from, like why should you believe me? Over 20 years of brazing every day (silver and brass) in a production environment. Not an expert, as in I didn't get an advanced degree in the science of it or anything, but 20 years of practice did give me some clue as to what's going on. Most of that time I used both acetylene and propane, like evey day, so I'm very familiar with the differences between them. Propane, with the right tips, now suffices for everything acetylene can do, short of gas-welding of steel, which I never do. (If I want to weld, I have TIG.) I now believe there's no good reason for anyone to use acetylene anymore, though YMMV.
P1040129 by nessism, on Flickr
