In article , Dave August says...

You can get a Sievert/Goss porpane/air torch that will make the biggest O/A
rosebud you have look like a joke as far as BTU/s go.
I've done silver braising work with both O/A and propane and I'd take the
propane any day. Theses ain't some wimpy 'Bernz-o-matic' thingies on the end
of a can you hold in your hand,. Were talking serious torch here, I've seen
some of these 'weed burners' with 6 inch bell that will put out some serious
heat. The trouble with O/A is it's way too hot but dosen't have the BTU's.

My experience with any torch that runs on air is that there's a
lot of nitrogen along for the ride, and it winds up flowing a *lot*
of gas to get the fuel/air mix right. And this tends to blow away
the flux.

I certianly agree with Dan on the sil-phos approch to copper. I build copper
boilers for 1/8 scale live steam. Were talking serious copper here, 6 or 8
inch Schedule 40, 4 or 5 feet long, with 20+ 3/4 inch flues and 10 pounds
of copper bar in the mud ring, theres a LOT of mass to keep hot.. My local
welding supply house has a Uniweld product UNI-1000 that I use. Same deal as
Sil-phos, 0% silver, %7Phosphorus, %93 Copper.. The stuff is magic on
Copper, no flux, runs like water at 1470 deg.. Works on close joints too
(.001 inch). The nice thing is after the first hydro, when you find the
leaks,

Leaks? What are those?



you don't have to pickle and flux it, ya just heat it up again and go
in with the rod. I've also done traditional Silver braising work building
up 'weldmenst' out of brass or steal for things like cylinders etc using
high content silver %65-%75.. stick with the Propane, you'll be happier in
the long run.

Obviously you are doing *big* stuff - and have found the tool that works
best for the job, namely getting a big part up to temperature. For
small work that I hand-flux, I like the OA torch. No pickling required
because once the borax flux comes off, it's pretty clean.

Jim


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