One of the things I struggle with is I mostly have used Air Acetylene in the last several years, and also a lot of MapPro and SB8. But recently I've found that there are just more things that are easily done with OA, and you can get in and out quickly. Brazing 7/8" with Air Acet is a big problem for me, you have to use a big tip and that puts all kinds of heat out around the braze. I tried using it on a split system with the condenser close to the house, which was brick and I got so hot in between the unit and the house it was amazing. That's when I broke out the OA, went in got it done and was out before the heat had a chance to build up like that. Trouble is, I hadn't used OA for a while and I really think I was trying to run the pressures kind of on the low side for a #2 tip and it just doesn't control well that low ~2-3psi on act. Sooo, I'be been here in the shop messing around and running 3-5psi and slightly reducing flame and it seems to be holding the flame where i set it. I've also been letting the torch run a bit longer before starting work, so that the gas pressure in the lines evens out to the settings and that may have helped some. Another thing I've been doing, which I never did in the past was to set the pressures on the regs where they should be and try to use the torch valves to handle the mix. That also seems to work better for keeping the flame stable where it's set.
I dunno, I just hadn't had to mess with OA for a while and needed to get back in practice. i have the same Victor set pictured in a previous thread, and I think it's a decent set for what I need, it's about 6 years old and seen a lot of use in the beginning, just not so much lately.
As to brazing 7/8" with a #2 tip, I think it works great, just throw some heat to it and go, then when you've gone all around, a little playing of the heat to suck it in the cup and smooth out the fillet and you're done. In fact while I was playing around in the shop, I brazed a 7/8" stub, and used Wet Rag putty maybe 2-1/2" back, right against the cup, with a temp probe on the other side, just to see. I'd seen it done before but never tried it. The probe was maybe 3-1/2" from the braze and never go above 178*F, and I deliberately took longer to braze than was humanly necessary to give it a good test. That stuff has always worked for me, but I had never really checked to see just how much heat it blocked, other than by touching it after a few minutes. i always put a wet rag over the braze after a few minutes and cool everything down.
Oh well, I guess even an old dog needs to keep up on his technique and keep in practice. Of all the things I do with heat, i use MapPro when I can on refrigeration, even though it actually takes more finesse than any brazing. But my favorite way to braze is OA, it's just the easiest way to heat it and get er done and get out.
I'm still confused over the withdrawl rate of act from small bottles, even though I use a B tank with oxy. There's not a lot of room above a #2 tip on those small bottles, but yet my MC outfit came with a cutting torch, go figure, there's not way to stay within the withdraw rate with that sucker! Even a #2 Victor tip set at it's lowest (3psi), uses 1/8 of a B tank an hour, and at it's highest (5psi), it uses 1/25 of a B tank per hour. I know for a fact that a lot, and I mean a lot of guys use rosebuds for brazing with even MC tanks, and I've seen a fellow or two that used a cutting torch head, (not using the O2 lever of course) for brazing copper with a B tank IIRC !!!
I wish the manufacturers would flatly state what is acceptable and what is not, but then the liability kicks in and everything goes haywire. I guess they've protected themselves with the 1/10 rule and that gives them the protection they need from lawyers. Even though we all know of situations of use that goes way beyond that and seemingly no problems.
