I'm in the market for a mapp/air torch, and I notice that the new ones (Bernzomatic, BZ8250 in particular) use a stainless steel burner. I've always seen brass used in a torch end, from propane up to oxy/acetylene setups, and I am wondering if stainless is such a good idea for the application.
I do know that stainless and brass have similar melting points, but I've seen stainless "rust" that after being exposed to hot/cold cycles (barbeque burner).
Is my concern for the longevity of a stainless steel burner tip warranted?
I've used my MAPP torch set enough over the years, that if the burner tube was subject to quick or even steady, slow erosion, it would've happened by now, Jon.
I often run the fuel rate high enough to make the tube glow red (pretty much wide open at the tank-top regulator valve), and it hasn't eroded much, if any. It hasn't left any deep pits, or caused flaking of the SS.
I bought it at Sears, over 10 years ago (crap, maybe 20) and didn't expect it to be a long-lasting torch, but it has been. I can probably count the tools I've bought at Sears during that time on one hand, but as we know, Sears doesn't manufacture anything but receipts and flimsy, sometimes worthwhile warranties.
I guess the accurate answer is YMMV, as I have no idea what alloy the SS is, or what materials are used in newer torches.
Even though some users will state that MAPP can't be used to braze steel, the large one I have will do this, and I'm talking about steel bar stock, not little strips of sheet metal.
This particular set included 2 torches that screw into the tank top regulator, a light duty one about the same diameter as a common yellow pencil, and a larger one. I keep soft vacuum caps (the caps that are sold at auto parts stores for capping off vacuum fittings) to keep dirt out of the inlets/jets (and likewise covers on the tops of the tank fittings).
You can do steel brazing with propane - one of those swirl-torch gadgets. It's got to be fairly small, and the bottle gets cold (and empty) pretty quick, but it sure is handy for small jobs on a sunday - many places that are open will have propane.
I'll offer some more description about the screw-on disposable tank-type MAPP torch I've been using. The MAPP gas is meant to mix and burn within the burner tube on all of them of this type that I've seen. I know this seems weird, but the opening in the bigger mixer/burner "tip" that I have is about 3/8" diameter. The last 2" of tube is where the combustion begins.
I don't have any experience with a refillable cylinder, regulator and hose type MAPP/air torch. I dunno if the construction has any similarities to the screw-on type torch.
The orifice/jet is located at the base of the tube at a venturi (with considerably larger air holes than a propane torch) where the gas flow draws in air, then there is a twisted helix of sheet metal within the tube, which I think is intended to swirl the mix to ensure that the air and the MAPP gas are mixed.
Combustion begins to take place within the burner tube (in the last 2" of length), which is why the end of the tube glows. Most of the flame that exits the tube is blue, and extends quite a ways past the tube end, especially when the regulator valve adjustment is close to wide open.
The smaller mixer/burner "tip" looks more like a conventional cutting torch tip, only at the end, except the fluted center is set back inside about 1/8" from the end of the stainless steel tube. For this smaller tube, the combustion takes place outside/just beyond the end of the fluted insert, so there is no red glow from the smaller tube/tip.
It should be mentioned here again, that connecting a MAPP gas tank to a regular propane torch won't result in the same heat output as when MAPP gas is used with a MAPP torch. I haven't measured the temperature or heat output, but the performance is about the same as just using propane, when using a propane torch. As mentioned above, the air intake holes/ports at the venturi are much larger on a MAPP torch, suggesting that the gas/air balance is a lot different.
Propane will also work for those zinc/aluminum-miracle-repair type rods, but MAPP is much better in that there isn't so much time (and fuel) wasted to get numerous connections or joints done quickly.
I've had fabricating projects where the aluminum repair rods were used for numerous joints using 1/8"x1" aluminum angle, and since aluminum dissipates heat so quickly, using propane would've been miserably slow, if it could have even been finished at all.
Back in my college days in the 1970s I put food on the table and gas in the tank by repairing golf clubs. Used a propane torch about 2 hours a day and had one I think was called a "turbo torch" or "tornado torch" or something. it had a stainless steel tube and did burn inside the tube. I went through a couple of bottles of propane a week and never had any noticeable erosion of the tube in the 4 or 5 years I used it.
Hmm ... my own experience, using the same torch, but starting with a tank of propane, and then switching to a tank of MAPP, that I could do small silver soldering with the MAPP, but not with the propane, which suggests a bit more heat available from the MAPP -- whether it is a higher flame temperature, or just better transfer of energy to the workpiece remains to be seen. The workpiece was not surrounded by firebrick (I don't have any, yet), and it had to be clamped in a drill press vise, with the second part held on with some copper wire while the silver solder flowed.
It might simply be that the MAPP torch in question is designed to burn more fuel per unit time, so it needs more air for that.
Jon, Brass melts at about 1980 F. SS melts well above 3100 F, some alloys like XB and inconel are even higher. That's why SS is used in blast furnaces as rolls, muffels and flame venturis. Your copper alloys are used to wick away the heat into the torch body, which they do much better than SS. Steve
Thanks Steve, and you're right (I was looking up Al/Brass just before the SS number, which let to my confusion). I did notice that the SS torch had a longer tube extending from the plastic handle; perhaps that gives it the additional distance to cool itself off.
About the only thing I don't like about the newer (stainless) torch is that the air inlet ports are a part of the plastic handle, whereas on the old brass unit they were upwards of the plastic handle, part of the metal just before the burn area.
I can't help but think that when the plastic breaks, the newer model is gonna be SOL, whereas on the old one, I'd just have to cobble up a new handle and reconnect the hose.
while we're on the subject of brazing and temperatures.... I recently had one heck of a time doing some brazing on a section of exhaust pipe. I have a bernzomatic mapp torch(pietzo w/ swirl tip) and it was barely hot enough to get the bronze to flow. the repair was chunky and incomplete. I gave up and used an old hobby size oxy/mps(mapp) torch(also Bernzomatic, the kind that uses the small cylinders, the oxy last only a few minutes and costs $10 a pop). I used the mapp (swirl) torch as preheat. still had difficulty.
now, I recall a few yrs ago my father had a brazing kit(Motomaster? CanadianTire brand) with a bottle of "brazing fuel" with a "brazing torch". it wasn't a swirl tip(rather it was long, bent, SS, rounded in at the end), but it seemed hotter and easier to braze with, unfortunately it was used up. the bottle was black, and just labeled "brazing fuel". anywhere I ask about such an animal I'm always told it was probably mapp.... but I don't get the same results using ye old yellow bottles and the self-same "brazing torch" I'd rather not have to go more industrial and buy a $400 pair of tanks for my here-to unused Harris torch kit(bought yrs ago, never used), just so I can do a little brazing from time to time. most of the work I do is mig, so I find it hard to justify the tanks.
sugestions? could the rod be the problem? too high a grade?
The usual color (in the US) for acetylene tanks is black, Mark. There are some common types of acetylene/air torches used in the HVAC trade to braze AC lines.
With air introduced into the acetylene flow path, it will burn very hot without making a lot of fluffy soot, like it does when the oxygen is turned off using an oxy/acetylene torch.
MAPP is becoming available in large bottles, but I've only used the disposable type small bottles.
I vaguely recall seeing a comparison chart showing various industrial fuel gasses and their heat output values. Some searching would probably find something similar.
MAPP gas is liquefied petroleum gas (LPG) mixed with methylacetylene-propadiene. In Australia, it is known as RazorGas.. (wikipedia)
I'd rather not have to go more industrial and buy a $400 pair of tanks for my here-to unused Harris torch kit(bought yrs ago, never used), just so I can do a little brazing from time to time. most of the work I do is mig, so I find it hard to justify the tanks.
sugestions? could the rod be the problem? too high a grade?
t.i.a.
-mark
I think you will find that $ spent getting your oxyacetolyene torch able to work will be $ well spent - it is much faster, easier, and more versatile than propane/mapp
Those are both a joke - the Bernzomatic is like One Cubic Foot of Oxygen compressed at a few hundred PSI, totally worthless. And the Oxygen Generator that took the pyrolytic sticks are just as worthless.
Air-Acetylene torch, sold for plumbers and pipefitters - Prestolite being the most popular. Comes with the ~50 CF "B" Acetylene bottle, the smallest practical home bottle. I've done a LOT of silver braze with one where my boss said I needed Oxygen. Not if you know what you're doing...
(The ~10 CF "MC" Acetylene cylinder is another waste of time - since you can only withdraw 1/7 capacity per hour, the flow is too small for anything other than a motorcycle headlight - which for some fascinating reason is why it's called a MC Cylinder.)
You don't need to get the lease sized 200CF industrial tanks - a
50CF Oxygen and a B Acetylene should set you back $250 purchased brand new and filled, a LOT less if you haunt garage sales and pick up a used set. And they are yours forever - the smaller tanks are always owned.
( The big ones can be owned or leased, and that's where keeping the paperwork is important. Because if the tanks have a neck collar for a local supply house and you can't come up with the paperwork that says you own a set when you take them in for a refill, they can take them back as stolen.... )
Harris and others make Air-Acetylene torch handles and tips, and they can be used with any welding regulator and tank. So you don't have to find an 'Antique' Prestolite.
Just be careful - Read up on care and feeding of bottles. Go slamming and banging them around and break the matrix inside the acetylene bottle, and they can't be refilled and must be destroyed. Can't let the acetone get out or contact between acetylene and pure copper - copper acetylide salts go BOOM. Can't let line pressure rise above 15 PSI outside the cylinder, or the gas can go BOOM! Must have arrestors in the gas lines, let that shockwave get back to the tank, and the BOOM! gets real big.
Oxygen can't be treated cavalierly either - Can't get any oil or grease at ALL In the Oxygen path that isn't specially formulated for the use (and used in controlled quantities) or it can make mayhem too.
And sometimes when the surface you are trying to braze will not tin for nothing or nobody, you have to get it hot /then/ scrub it down with more flux and a stainless wire brush. And all of a sudden it decides to clean up and wet with a vengeance.
now, I recall a few yrs ago my father had a brazing kit(Motomaster? CanadianTire brand) with a bottle of "brazing fuel" with a "brazing torch". it wasn't a swirl tip(rather it was long, bent, SS, rounded in at the end), but it seemed hotter and easier to braze with, unfortunately it was used up. the bottle was black, and just labeled "brazing fuel". anywhere I ask about such an animal I'm always told it was probably mapp.... but I don't get the same results using ye old yellow bottles and the self-same "brazing torch" I'd rather not have to go more industrial and buy a $400 pair of tanks for my here-to unused Harris torch kit(bought yrs ago, never used), just so I can do a little brazing from time to time. most of the work I do is mig, so I find it hard to justify the tanks.
sugestions? could the rod be the problem? too high a grade?
Well, I am not a welder (IANAW), but in my "research" for this torch I found these guys using the previous version of the Bernzomatic (JTH7 - Mapp/Air) to build bicycle frames:
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So, at least from those guys, mapp/air can be used to braze.
In any case, it looks like I'm probably going to pick up the newer version mapp/air torch. I noticed that the forge guy is using one on his mini-forge, and seems to like it better than the old one, which is good enough for me.
I'm fairly certain that this particular model of MAPP torch that I've been using has a higher fuel delivery/burn rate than any propane torch I've used, since the length of the blue flame extending from the swirl chamber/tip is much larger diameter, longer and louder than with any propane torch.
I suspect that there are many variations in the designs of all the available portable torches. I see some propane torches at stores now with huge burner heads on them (over 1" diameter), when years ago, they all looked about the same.
I haven't looked, but I would doubt that there are any readily available specifications available for orifice sizes or CFH cu-ft/hour rates for these portable torches.
My original reply was YMMV, as I would expect that there are many differences in portable torches, especially related to cool-looking and cheaper to manufacture products.
I have a couple of types of these, I only use propane in them, though, I have O/A equipment for the really hot requirements. On one, the burner will glow dull red after extended running, it's a "turbo" or "tornado" type of burner, and even with propane, it's much hotter than the older 50s-60s Bernzomatic-style burners. Those old ones just got stuffed in the bottom of an old tool box. All that happens with the stainless burners is that they get a nice blue color, which doesn't affect functioning at all. Unless you use it 24/7, I think your concerns are groundless. I've got one I've used extensively for 10 years.
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