Using Oxy-acetylene with propane to weld steel with an aluminum TIG rod & putty knife

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How could this NOT work well?Just sharing a story of last weekend...I do have some questions at the end.I tried everything, and I just could NOT fill in the holes in my motorcycle exhaust headers with my HF AC stick welder. I'd cut out a patch, try to weld it on, burn through, and make a mess of everything. Finally I got it to the point where it had a bunch of little holes, instead of big holes. I plugged the ends of the header pipe and blew smoke from a cigar into the header to see where the smoke came out to find the holes. Answer: pretty much everwhere I'd welded. So, I look around the shop for some options. I have a dirt cheap Chinese deathtrap Oxy-Acetylene rig I got new on ebay for $80. I have an oxygen tank and some propane tanks for a grill. I don't have any brazing rods, so I search around for some wire coat hangers. I only could find plastic--but I do have some zinc-based (I think) aluminum soldering rods, as well as some TIG aluminum rods (No, I don't own, nor will I ever probably own a TIG machine. I can't remember why I have the rods).After trying several different methods of oxy-fuel welding and/or heating, here's what worked best: I'd use the rosebud attachment to heat the header pipe up to a bright shiny red and melt a big blob of aluminum on top of it. While keeping the puddle hot with the torch, my friend used a metal putty knife to press the AL into the holes and gaps, just like you'd do with spackling in drywall. Did this all around the pipe, let it cool, and blew more smoke inside. Vast improvement! It still leaks, but not nearly as much! Wrap it up in some kitchen aluminum foil and then wrap it with exhaust heat wrapping tape, and no one should ever be able to tell what a horrible job I did--which qualifies as a success in my book.Okay, I'm not a complete idiot. I know you can't weld aluminum to steel. And I know oxy-propane welding is the worst idea for just about anything (especially with acetylene hoses and regulators). I didn't expect it to work at all. But it did work reasonably well for my low standards, by melting the TIG rod into the cracks. (I guess that's still considered brazing since it's done at like 1200*, even though I'm not joining things together? Or is there another term for it?)Anyway...here's my question. If I had done this technique with the correct stuff, such as a flux-coated bronze brazing rod, would it have worked well? Or would it shrink and crack and fall out? Or would I just have melted my putty knife? Do people use putty/spackling techniques like this when brazing/soldering? Would it have worked if I'd found some coat hangers? What's the melting point of a coat hanger, anyway?"To tell which polarity to use go to the bathroom and pour some water down the drain. If it runs clockwise use straight polarity. If it runs counter-clockwise use reverse polarity. Or if it just gurgles use alternating current." -RandomDave
Reply:I am no stranger to improvisation and "making do", and I really applaud your efforts. On another note - I think your going to hurt yourself. Put the project aside and seriously practice with some tried and true techniques and methods before you go tackling MC or auto repair. Books on welding / brazing / soldering are plentiful, the internet is "free". Hood time is the best way to learn - but it sounds like you need some fundamentals to build upon. Again - I am not trying to be a jerk or come across like I know it all, but there is a reason that most answers to the simple problems posted here are almost identical from member to member. Be careful - but keep at it. Regards, ChrisJust another clown trying to be cool
Reply:Originally Posted by jinkzdI am no stranger to improvisation and "making do", and I really applaud your efforts. On another note - I think your going to hurt yourself. Put the project aside and seriously practice with some tried and true techniques and methods before you go tackling MC or auto repair. Books on welding / brazing / soldering are plentiful, the internet is "free". Hood time is the best way to learn - but it sounds like you need some fundamentals to build upon. Again - I am not trying to be a jerk or come across like I know it all, but there is a reason that most answers to the simple problems posted here are almost identical from member to member. Be careful - but keep at it. Regards, Chris
Reply:I'll assume you are serious, and not making some bad joke. There's just so many things wrong with this I don't know where to start.My 1st thought is the welding police should show up at your place and just take away your stuff. You've just got the wrong outlook on this from so many angles. The definition "HACK" probably's going to have your pict next to it if you keep this up.Let's look at the issues here.#1 Stick is a poor choice for thin steel like exhaust work. Stick with a POS 110v machine is even harder than it needs to be.#2 Your attempt at "brazing" is a joke at best. All you've really done is mush metal in the holes. High temp epoxy putty would have done the same thing except it sticks to steel and would seal better.#3 if you're going to wrap it all in exhaust wrap, why just start off with that to begin with.I could see if you were out on a trail and needed to get back where some of this might apply, but you could just run it open at that point also. This doesn't sound like an "emergency repair" Why just post BS cr@p like this?You seriously need to spend time learning. Start out with getting a decent used Tombstone and learn to stick weld if thats the direction you want to go. If you want to stay cheap and 110v, at least get a POS mig as opposed to that POS stick machine. I'd suggest mig with gas over a 110v FC machine, because thin steel with FC is almost as tough as stick many times. At least with mig/FC you will simplify things on thin steel.If you plan on sticking with the POS stick, then lay in a basic supply of brazing rod and some flux. I'd suggest that over the prefluxed sticks, but I've used them in a pinch. Your Oxy fuel rig is probably fine for doing general brazing. I used Oxy fuel for all sorts of repairs when I only had a stick machine and wanted to do thin steel. I've still got a small tube of brazing rods and the can of flux on the shelf "just in case" as well as a few packs of misc prefluxed silsolder and brazing rods that I nabbed from a hardware store that was closing. You could probably have done a decent job with brazing rod and this wouldn't look like a joke.I'm not trying to be harsh, even though it probably sounds that way. The "it's ugly but it holds" is BS. If you want to learn, then learn to do it right. That or just don't bother to post. Practice, practice, practice... You've already handicapped yourself with your choice of a machine. The only way to overcome that handicap is to spend a lot of extra time learning to do it right so you can compensate for the issues it has. Go buy 20 lbs of 1/16" or 3/32" rod, what ever size that little machine runs well and some 3/16" plate or angle and start running beads. If you can get it get 6013 or 7014 for that machine, it will be easier to learn than with 6011 or 7018 to start.I'd suggest you start with the angle like a V and add a couple feet so it stays in that position ans start filling that V up. Run the beads so that they overlap by 1/2 and build this up in layers. It's called padding. You can do the same thing on a decent sized flat plate say 4-6" wide as well. Run the beads right on top of each other and try to keep things as smooth as possible. I'll see if I've got a chunk I was letting my buddy's nephew play with in the garage tomorrow and post picts. When you can control that, then you can lay the angle over like an L and fill that one up working on horizontal, then stand it up and run verticals after that. After 100lbs or so of rod you'll probably start to get the hang of this.I'm not joking about the 100lbs of rod. 1 or 2 pounds won't cut it. Running 5 or 6 beads won't teach you much. If you want to learn, you need to run beads, and LOTS of them. I still grab a chunk of scrap and run practice beads every time I need to run stick. I don't use it enough to keep my hand in. The practice runs let me get my settings right, and get back in the swing of the movements and travel speed. I was doing a bit today since it was too windy to use my mig and I wanted to get some things prepped for Monday. If I have a job that has to be done in stick and needs to be more than a few tacks, I'll plan to burn 5-10 lbs of practice rods so I've got things down cold again. Post up picts of the good, the bad, and the ugly as well as info on thickness of steel, rod size and type and settings and we'll help you learn if thats what you want..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Skippii dude.You sure have put up some  posts in the last couple of days.I agree with DSW, learn proper methods and technique first before you teach yourself to be a full time hack with a lot of bad habbits to get rid of.Dont say you will never own a TIG.  I said that 10 or so years ago.
Reply:Originally Posted by DSWI'll assume you are serious, and not making some bad joke. There's just so many things wrong with this I don't know where to start.
Reply:The answer to your question would be, no.You will probably find that the exhaust temp will melt what you did out.Bronze would also not be suitable for exhaust.    The only time ive seen/used such a technique is when lead filling/shaping on body panels.