I read JasonGrahn's thread "learning to weld" with much interest. There are a lot of you board members who know their stuff about welding so I wanted to ask:
Can mapp gas (sold in yellow cylinders in hardware stores) be used to braze or weld exhaust tubing if I wanted to modify or fabricate my own exhaust system? I know it won't be of professional quality but as long as I can do it without having exhaust gases leaking I thought I might give it a try one of these years.
And if it can be done, would I have to go through too many mapp gas cylinders to make it practical (cost-wise)?
Years ago, a welder-friend of mine gave me some basic instruction and let me practice welding. He said I did a decent job. It would have been good except for a pinhole in one of the practice samples and the fact that it didn't look really "clean" as a professional would have done it.
mapp gas brazing/welding
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mapp gas brazing/welding
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vrg3
- Vikash
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It can, but those tiny cylinders sold at the hardware store aren't very useful. Each canister of MAPP burns four canisters of oxygen. And you might not get much more than a single brazed pipe joint out of one canister of MAPP. A long time ago (back when I was much more of a novice than I am now), it took me one and a half cans just to braze an oil return fitting on an oil pan.
I think you're better off renting an actual torch welding outfit. Even if you plan to braze, I find it easier to braze with oxy-acetylene than oxy-MAPP. But a real oxy-MAPP setup should do fine too.
If you plan to weld, you may be better off with arc welding. TIG allows you to make pretty clean welds and isn't all that different from torch welding.
I think you're better off renting an actual torch welding outfit. Even if you plan to braze, I find it easier to braze with oxy-acetylene than oxy-MAPP. But a real oxy-MAPP setup should do fine too.
If you plan to weld, you may be better off with arc welding. TIG allows you to make pretty clean welds and isn't all that different from torch welding.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
For exhaust stuff, I'd probably recommend against brazing due to the high temps.
Josh
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surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT
If you need to get a hold of me please email me rather then pm
a small MIG welder would be your best cost-effective solution for exhausts. Not quite as pretty on the welds as TIG but a tig rig is out of reach for the hobby welder.
You can probably find a good used MIG for a couple hundred locally. try to get the most powerful that will run on house current, and if you can get lots of goodies like extra wire, tanks (the gas is different for aluminum), etc so much the better
migs are great for bodywork metal repairs also. small home units won't do steel over about 1/8" thick very well, but there isn't much of that on cars anyway
You can probably find a good used MIG for a couple hundred locally. try to get the most powerful that will run on house current, and if you can get lots of goodies like extra wire, tanks (the gas is different for aluminum), etc so much the better
migs are great for bodywork metal repairs also. small home units won't do steel over about 1/8" thick very well, but there isn't much of that on cars anyway
That beer you are drinking cost more than my car
dont even waste your time trying to braze an exhaust. not strong enough unless you have lug'd fittings to use, which you wont. I guess you could make it out of sch. 40 pipe 
exhausts are MIG'd.
look for a used millermatic 135 or something of that nature, talk with your local welding shop and they can get you set up. but be ready for some sticker shock on the new machines. then go to the exhaust shop and grab a variety of scrap tubing to practice on. they should give it to you for free.
renting is an option, but rent one enough times and you could have bought your own. I havent checked but I bet its like $40 a day.
for really cheap(~$150), you can use one of the shitty flux core only welders,(no gas) but they are harder to wrok with especially for the beginner and turn out crappier, weaker, uglier welds. you are much better off spending the few hundred on a quality unit, which will make your learning curve much flatter.
always use very good prep. this means grinding clean all surfaces to be welded. especially with anything galvanized. you do NOT want to be inhaling zinc oxide.
get a chart of what wire speed/amps/wire size to use for which thickness of metal.
get a welding hood with a large window(4x5 is the big size I think), or an auto darkening. harbor freight has a so-so one of these for ~$80.
see if your local community college has a welding program. if they do, take the class. should be about $300. they will have a huge shop with a varitey of expensive ass welders and equipment, and great instruction which is definitely the biggest thing. it is almost worth paying the tuition just to use the shop. for instance, south seattle community college has a bunch of brand new miller TIGs and MIGs, a bunch of really nice heavy fab equipment from boeing, a hydraulic tube bender with about 20 sets of dies(BIG bucks) and everything you could ever want for making stuff.
fabricating is fun.
exhausts are MIG'd.look for a used millermatic 135 or something of that nature, talk with your local welding shop and they can get you set up. but be ready for some sticker shock on the new machines. then go to the exhaust shop and grab a variety of scrap tubing to practice on. they should give it to you for free.
renting is an option, but rent one enough times and you could have bought your own. I havent checked but I bet its like $40 a day.
for really cheap(~$150), you can use one of the shitty flux core only welders,(no gas) but they are harder to wrok with especially for the beginner and turn out crappier, weaker, uglier welds. you are much better off spending the few hundred on a quality unit, which will make your learning curve much flatter.
always use very good prep. this means grinding clean all surfaces to be welded. especially with anything galvanized. you do NOT want to be inhaling zinc oxide.
get a chart of what wire speed/amps/wire size to use for which thickness of metal.
get a welding hood with a large window(4x5 is the big size I think), or an auto darkening. harbor freight has a so-so one of these for ~$80.
see if your local community college has a welding program. if they do, take the class. should be about $300. they will have a huge shop with a varitey of expensive ass welders and equipment, and great instruction which is definitely the biggest thing. it is almost worth paying the tuition just to use the shop. for instance, south seattle community college has a bunch of brand new miller TIGs and MIGs, a bunch of really nice heavy fab equipment from boeing, a hydraulic tube bender with about 20 sets of dies(BIG bucks) and everything you could ever want for making stuff.
fabricating is fun.
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