over-head welding Help!

[uhcrandy]

I have been learning, on my own, welding. How do you guys do "overhead welding"? I have done a couple of exhaust sysytems, and need to do a little overhead welding, and it looks like s**t, or I burn through...Arrg! One thing I have learned is what a good craftsman can do. I like to inspect every weld I see.
How do you all do it?

 

[DEEDDUDE]

Kinda hard to explain typing, but i guess the biggest thing to remember is to not keep your rod/wire in one spot for too long. When stick welding i like to move the stick end in a "J" shape, depositing weld materal and moving the stick out of the puddle then back into the puddle alternating the hook of the "J". Mig would be similar.

 

[koditten]

I pretty much "spot weld" with the MIG unit for exhaust pipe. Heavier stuff is easier to carry a bead. I still make shorter welds. I don't try to make the whole weld in one pass.

KO

 

[camjeep3]

its not fun, especially when learning, once you figure it out it is tolerable. the best advice is get as comfortable as possible. Relax and BREATH be steady(yes this is hard). If you are running exhaust turn it down and stay out of the middle of the joint. and prob run pretty quick.

 

[Zeke]

Turn the heat down 10% and try that. Don't let the puddle get too big and have gravity take over.

 

[d_rock]

adjust your stick out so its close to the end of your cup. keep the cup close to your work. I like to actually turn the heat and wire feed up a bit and weld a little faster then I normally would. do some test passes to make sure you can make the pass without starting and stoping. When first starting out you might want to get yourself a welding blanket to hide under. and the best advice I can give is practice practice practice.

 

[rsanter]

Practice, get your heat and feed rate correct and there shouldn't be a problem.
Weld a 1/2" bead at a time with a pause to allow the weld to cool from red to a dull brown and continue.

Bob

 

[laser3kw]

Weld a 1/2" bead at a time with a pause to allow the weld to cool from red to a dull brown and continue.

That's it^^^^^^
patience, slow and easy, a little at a time. Or tack, remove, finish on the bench, reinstall. Sometimes it takes less time and gives better results.

 

[Murphy4570]

Welding exhaust is easy, I do it every day.

If your using a MIG/FCAW welder, it is a cakewalk. Just keep the amps low enough that you can build and maintain a puddle without blowing through. Exhaust pipe is typically 1/16-1/8" thick, so it doesn't take much heat to penetrate the metal fully.

If your using a stick welder, good luck! Thin rod and low amps combined with going fast will keep you from blowing holes. Don't try using alternating current for overhead stuff.

 

[justanengineer]

I pretty much "spot weld" with the MIG unit for exhaust pipe.

^^^This. For exhaust there is no point in doing more than a few tacks. Your joints should be reasonably tight already and will fill with soot quickly. Tacking the joints also allows the exhaust to be disassembled fairly quickly/easily for future repair.

As for overhead welding, sounds like youre describing two similar situations. Either the weld is ugly (assuming the puddle is dripping due to gravity) or youre burning through. Irregardless, turn the heat down, turn the filler down, and/or speed up...some combination therein.

 

[Murphy4570]

^^^This. For exhaust there is no point in doing more than a few tacks. Your joints should be reasonably tight already and will fill with soot quickly. Tacking the joints also allows the exhaust to be disassembled fairly quickly/easily for future repair.

I disagree. It'll leak! That's no bueno.

Disassembly involves a sawzall, or hand tools and the blue wrench if you fabricated flanges throughout the system when you built it. I'm talking custom bent piping here, not that "pre-bent" **** they sell at parts stores. That stuff doesn't fit worth a damn half the time, and rusts out VERY fast. Only pre-bent stuff I regularly use is tailpipes for Jeep Wranglers/Cherokees, and Mustangs.

You can either weld, or clamp exhaust piping. Leaks of any kind are not to be tolerated. A leak near an oxygen sensor will throw off the reading it sends to the ECM, and cause problems. A leak somewhere else will cause noise at best, or allow carbon monoxide to enter into the vehicle's cabin at worst.

 

[Herb]

HaHa! Beware the Grapes of Wrath!

 

[justanengineer]

I disagree. It'll leak! That's no bueno.

No they dont. If they did, Id have codes popping all over the place on my vehicles and/or had many complaints in the past. Ive built quite a few exhaust systems and after 30 mins run time any minor leaks are tight and solid. The key is to build it carefully, and as you said dont use cheap store bought bends. All of mine are done with a bender and an expander. You expand the upstream end, and when the two pieces are stuck together by hand, the joint should be rather difficult to pull back apart, similar to how a machine taper quickly locks together. Realistically, its a low pressure system, the welds shouldnt be a stress point carrying any weight, and if you think about the exhaust flow....if you expanded the correct end of the pipe, at each joint the flow would have to do a U-turn to leak vs flowing straight - the flow is working with you to prevent leaks. Also, if you consider an exhaust clamp, its not exactly a great seal.

You could fully weld each joint to cover shoddy fitment, but as you admit, you need a saw, a blue torch, and/or an hour or two to do a five minute job. If there's 2-3 tacks on each joint, 30 seconds with a grinder or hand file and each section can be easily removed.

 

[d_rock]

I disagree. It'll leak! That's no bueno.

Disassembly involves a sawzall, or hand tools and the blue wrench if you fabricated flanges throughout the system when you built it. I'm talking custom bent piping here, not that "pre-bent" **** they sell at parts stores. That stuff doesn't fit worth a damn half the time, and rusts out VERY fast. Only pre-bent stuff I regularly use is tailpipes for Jeep Wranglers/Cherokees, and Mustangs.

You can either weld, or clamp exhaust piping. Leaks of any kind are not to be tolerated. A leak near an oxygen sensor will throw off the reading it sends to the ECM, and cause problems. A leak somewhere else will cause noise at best, or allow carbon monoxide to enter into the vehicle's cabin at worst.

I agree with this guy. The only thing that should ever be spot welded together is sheet metal. people use spot welding and stitch welding when they don't know how to properly set there machine.

 

[Steevo]

The OP didn't state what kind of welding he is doing. Could be Oxy/Acet, could be MIG, could be stick.

 

[Kevin54]

To the OP.....are you building exhaust for a business where you work, or are you doing this at home?

Personally I don't care for a welded exhaust. That is the first place things start to go south as far as rust. I prefer clamping the exhaust with band clamps and impact the clamps down tight. If you have to take the exhaust apart anytime down the road, pull the clamp off and pull the pipes apart. And since using band clamps, I'll never use a standard "U" shaped clamp again. And what is nice about the band clamps it that the stainless steel clamp conforms to the different size of pipes.

 

[gorilla]

Many years ago I learned that fast and hot was needed for overhead welding. I passed the test for 1" plate so I know that method works.

 

[MG44]

No they dont. If they did, Id have codes popping all over the place on my vehicles and/or had many complaints in the past. Ive built quite a few exhaust systems and after 30 mins run time any minor leaks are tight and solid. The key is to build it carefully, and as you said dont use cheap store bought bends. All of mine are done with a bender and an expander. You expand the upstream end, and when the two pieces are stuck together by hand, the joint should be rather difficult to pull back apart, similar to how a machine taper quickly locks together. Realistically, its a low pressure system, the welds shouldnt be a stress point carrying any weight, and if you think about the exhaust flow....if you expanded the correct end of the pipe, at each joint the flow would have to do a U-turn to leak vs flowing straight - the flow is working with you to prevent leaks. Also, if you consider an exhaust clamp, its not exactly a great seal.

You could fully weld each joint to cover shoddy fitment, but as you admit, you need a saw, a blue torch, and/or an hour or two to do a five minute job. If there's 2-3 tacks on each joint, 30 seconds with a grinder or hand file and each section can be easily removed.

Stated like a true arm chair mechanic. If you are welding exhaust, it needs to be fully welded all the way around. Spot welding it is never going to seal it up. The general test I have the guys do for exhaust is turn the car on, have one person put their hand on the exhaust plugging it up. You will hear the exhaust out of the muffler weep hole, anywhere else is unacceptable and just a place for moisture to collect and rust out the joint and must be fixed.

I have over $14k wrapped up into my exhaust bender. No mater how carefully you try to expand pipe to fit snug, it will always leak with a clamp unless you put sealant on the ends of the pipe (annoying, adds up) and use a round clamp. Round clamps by themselves still leak without sealant, U Clamps just distort the pipe and leak. Spot welding is a no no.

If you are welding exhaust pipe and having a difficult time keeping it steady over head rest your arm against the lift. You may have to make a few passes as it is difficult to get a good weld overhead the first time around on thin exhaust. The great part is that it is just exhaust, and not anything structural, so just seal it up!

 

[Kevin54]

No mater how carefully you try to expand pipe to fit snug, it will always leak with a clamp unless you put sealant on the ends of the pipe (annoying, adds up) and use a round clamp. Round clamps by themselves still leak without sealant

If that's the case, mine should have leaked and it didn't, and there was no sealant used on it. In all my life, I have never seen any kind of sealant used on exhaust.

 

[MG44]

You've just never properly checked for a leak. I'm looking at our exhaust supply catalog with about 20 different brands of sealants, puttys, etc. You are in Ohio, I'm in Massillon Ohio. Bring it on over, I'll pull it on the lift and show you the leaks

In response to rusted joints being the first place that things go south. That is correct, the welded joint will rust before anything. Depending on the vehicle and application, we will coat the welds. A uncoated exhaust weld should get a few years before any problems, but if they car is going to be on the road for a while it is a good idea to coat.

 

[Murphy4570]

Stated like a true arm chair mechanic. If you are welding exhaust, it needs to be fully welded all the way around. Spot welding it is never going to seal it up. The general test I have the guys do for exhaust is turn the car on, have one person put their hand on the exhaust plugging it up. You will hear the exhaust out of the muffler weep hole, anywhere else is unacceptable and just a place for moisture to collect and rust out the joint and must be fixed.

I have over $14k wrapped up into my exhaust bender. No mater how carefully you try to expand pipe to fit snug, it will always leak with a clamp unless you put sealant on the ends of the pipe (annoying, adds up) and use a round clamp. Round clamps by themselves still leak without sealant, U Clamps just distort the pipe and leak. Spot welding is a no no.

If you are welding exhaust pipe and having a difficult time keeping it steady over head rest your arm against the lift. You may have to make a few passes as it is difficult to get a good weld overhead the first time around on thin exhaust. The great part is that it is just exhaust, and not anything structural, so just seal it up!

You are right on the money.

You must have a serious bender if it cost you $14K. The one my shop uses is an ancient Bend-Pak from 1983.

I agree about where the welds are being the first place that rusts out, but not the welds themselves. I have found that the welding heat burns off the aluminized coating on the new exhaust pipe right there, so that metal rusts out faster than the rest which is still coated. We use Lincoln 110V welders with flux-core wire, works OK. I have used a MIG welder too, but find that it can be hard to weld in tight spots with it, and it is harder to lay a good weld bead sometimes, takes more finesse and skill.

 

[djjsr]

I'll have to try that "tack it and let it fill with soot" method. Never heard that before.

I've been screwing around with cars for 50 years and I learned something new today.

Thanks.

 

[MG44]

You are right on the money.

You must have a serious bender if it cost you $14K. The one my shop uses is an ancient Bend-Pak from 1983.

Its not quite $14k but damn near close in it. I have the top end Huth. Paid about $10,500 for it from the tool supplier, plus sales tax, plus interest (made payments), plus its been repaired a couple of times at our cost. Its tough to make your money back on exhaust with a big investment like that, and if I knew then what I know now, I wouldn't have spent nearly the kind of coin on an exhaust bender. New exhausts are much more durable then the stuff even 10 years ago. Its only nice for mounting universal mufflers, most converter and flex pipes just we don't even use it.

 

[uhcrandy]

Sorry I was less than Clear. I am using Flux-core .35 MIG. When I look at other Exhaust work, its a continuous weld, not tck welds. I like the idea of a continuous weld.
The welds that were done off the Jeep, look good. The under car weld not so much. Also the spatter hurts!! I am not a pro, just a shade-tree type.
Thanks for all your advice!

 

[bad_idea]

Painful weld spatter is fixed by wearing a welding jacket. Welding jacket will also help greatly with quality of weld. Easier to focus on the weld when you aren't dodging hot metal! .035 fluxcore is less than desirable for exhaust. It burns hot and you will have trouble with burn through. I would suggest .030 mig wire with 75/25 shielding gas. AND the very best way to in place welding is by removing it and doing it out of place! To HELL with in place welding! Hate it. Most things I weld I find a way to do it out of place. Are you able to tack the joint together in place and pull it out to weld it out of place?