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SmilinSam

Brazing vs Welding?

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SmilinSam
How hard is it to braze? Never tried before. Was wondering because its a pain to weld patches in rusted mower decks. The thinned metal is like trying to weld tinfoil. generally I weld the patch from the back side all around the edges which works fine overlapping from the thick to the thin. But from the otherside where the tin overlaps the thick its next to impossible without buring through. Thought maybe brazing would be a good way to clean up the rough edges on this side of the work...??..

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jrichason
Brazing might be a little easier since you just get the metal to the verge of forming a puddle, but I think you would still have problems with it heating up too fast on thin metal. Brazing does have the draw back of being more brittle. Plus you need to make sure you clean it up good if you are going to paint over it. When I gas weld on thin material I use the filler rod to shield the thin material from all the heat. Good luck, John

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PatRarick
Brazing does not work the best on rusted metal. You are not actually joining the metal, just "gluing" it together. Brazing is a lot like soldering, but is stronger, and requires more heat. Like soldering, the surface has to be free of rust in order for the brazing to stick. My experience on rusted decks or real thin metal, is much like John stated. There is a very fine line between getting the metal hot enough to accept the braze, and burning through it. The best luck I have had on repairing rusted decks, is a 110 volt wire feed. If you burn through, you can "click" the hole shut. Pat

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Dadsy98
My practice welding has been on mower decks. they all seem to develope cracks around the brackets in front. I have to tinker with the settings to get it just right. Even then I have burn throughs, particularly at the edges. I thought it would be a help if the feed and voltage controls were a foot pedal type. Then, I could adjust the arc and the heat on the fly. Steve

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jrichason
Wire feed has the additional benefit that you can hold a piece of brass behind it when welding to help prevent burning through. Eastwood has some with a handle that look pretty handy. I keep thinking I would like to learn how to TIG weld, but I haven't gotten around to it yet.

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jlasater
A copper block is best for backup up a weld, conducts heat better than brass. You'd need to use a flux core wire in a Mig gun to weld anything not clean as normal gas type mig setups don't have any cleaning action/no flux. I bought an IR "high speed sander" and mount 3M Roloc's on it, absolutely the best thing for making sure all the rust and other junk is off metal before welding. Wire brushing works good too, but the Roloc's really finish the job. Brazing is easiest if you try to match thicknesses of metal between the patch and what you're repairing, and matching the torch head as well. You don't need to braze with a rosebud tip :-) [img]http://www.jd40c.com/crawler/pictures/ir317.jpg[/img]

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Marion_Kerr
Sam, it's not difficult although you can knock the flux off of a welding rod and us it as a brazing rod. It's hard to get the brass brazing material to hold paint for a long period of time. After the metal is hot consentrate most of your torch heat on the rod itself and you won't burn-out the metal. Put your torch in one hand, the rod in the other at about 20 degree angles to each other forming a V. Keep the rod ahead of the torch flame and watch the "molten pool" of metal and you'll know what the quality of your weld is. I prefer to use metal rod anytime I can and stay away from the brazing. If you are welding cracks without addng plating. Drill the ends of the crack out so it doesn't continue, before welding.. Use a proper size brazing tip on your torch and you should be successful.. Set your guages at approx. the following, acetelyne= 8 lbs., oxygen= 40 lbs. Set your tip so it has a nice blue flame that is near perfect shape without any "points" of flame .. Hope this helps Sam.

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UCD
Sam As Marion said but the best rod I have used to fill or patch rusted or old panels is a wire coat hanger the heavy black ones prefered. I keep the metal just hot enough to make both pieces flow together useing the coat hanger as a filler rod. this was the only thing that worked on old rusty exhaust pipes till mig came along.

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Marion_Kerr
Believe it or not the "Quality" of coat hangers has changed in recent years. They make them out of a mix of all kinds of junk metal now and the welds made with them have no "tensil" strength and I don't find them very reliable or easy to make them look "good" like using a quality welding rod. You can buy long steel rods (about 30 to 36 inches long) at welding supply houses. They are usually right beside the brazing rods with the flux on them. The steel ones do not have flux since you don't need it for gas welding.

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HubbardRA
I own an AC "buzz box" that I uses for everything. This is most economical. I like the MIG welders, but a good one is expensive and a cheap one is not worth buying. I actually prefer gas welding for rust repair. Melt a gob of the rod onto the area to be joined, then work the gob down relatively level with the torch. As the surface of the metal starts to melt, the molten gob of will flatten out into that area. You cannot start the puddle in the base material without a burn through. This is a trick a mechanic taught me years ago for patching rusted exhaust pipes. Brasing will also work, but brass and steel are dissimilar metals. In the long run, galvanic corrosion will continue the problem. If I were going to braze in the pieces, I would coat the inside of the deck with plastic roof cement or some thick moisture resistant coating to prevent any moisture from getting to the area. Paint is not adequate.

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