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learn to weld volume 2 - advanced

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Old 12-17-2007, 04:03 AM   #1
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OK now that you know the basics, lets get into some more advanced welding help.

As always, safety first safety glasses, fire extinguisher, and gloves!

Sheet Metal...

Some of you want to do body work along with other welding. Sheet metal is tricky but not too hard. Unlike most welding, heat is your enemy here. Too much heat and you will warp your work. Not enough heat and your welds wont penetrate. Go to home depot and get some sheet metal approximately the the same thickness of the body panels you are goind to be working on. Cut some pieces off and try to weld them back in. This will allow you to get the heat and wire feed settings perfect.

Using flux core on sheet metal is possible, but it really gets to be a pain. Mostly because of the after weld clean up, and also because it tends to penetrate deeper. .025 wire is usually the biggest you want to use. I have used .035 flux core, and it can get bad, very fast . You want to just tack the pieces in. Start in the middle of the pieces and work out from there. Alternate sides, you want to make your tacks s far away from each other as possible. If you are welding in something small like an antenna filler, make a few tacks then let it cool a few minutes. Your tack weld should only last 1 - 2 seconds. Remember too much heat = bad news bears

There are a few tricks as well. As explained in the general welding basics thread, you can use a backing plate made from aluminum or brass. This is only good when you have access to the back of the weld. You can also use a damp rag. Wait for the weds to cool a little bit tho, ya dont want to burn the rag. There is also a putty product on the market that wicks heat away from the weld. I have never used it but I hear it is great.

Tool around a bit with the practice metal. Once you are comfortable get to work on yer ride!


Fitment is a crucial part of welding. Measure everything up, cut your steel a tad bit longer than you need it this way you can taylor it to fit. Tack your piece in place, this way you can make adjustments if need be. Its much easier to break a tack then cut out a weld.

Most of you will be welding steel, be it a frame, engine mounts, shock tabs, whatever.

First off, make sure the metal is clean. Rust can make for bad welds, grease and coatings can make bad. Now, if you are stick welding, you CAN weld on rust. You need to use a 7018 rod, it is good for welding crappy steel and runs like a champ!

Chamfering ensures that you get adequit penetration. Per ASME the proper weld chamfer angle is 35�, just make sure the is an angle . Chamfer your material that is going to be joined on all sides that will be welded. If you are going to make a butt weld, chamfer each piece. If you are going to make a lap weld chamfer the top piece, thogh this is not required. When making a T weld, chamfer the intersecting piece.

If for some reason you need to stop and then start again, be it for re positioning, more filler, beer break...whatever. Make sure you start your weld a little bit on the end of the previous weld. This will ensure there is no gap (weak spot) in the weld.

Heat settings are still critical, but a lot easier to set. Start at a midway setting and go from there. Its always easier to have a test piece but if you dont, this is a pretty safe way to go. if your material is thick, dont just hold the torch there and fill up the gap. Make multiple passes. lay a root weld down the center. Your next weld will be half way on the root weld, and half way on the bare metal. You can do this as many times as you want. Just make sure if you are going a bunch of these welds let the metal cool after you make a few. You can warp thick steel with too much heat. I have had to deal with fabricators that decided to stack like 8 weld passes back to back, and they warped 1-5/8" thick steel. Work smarter, not other words, take your time.

If you cut your metal a little too short, dont fret. Make a backing plate from aluminum or brass the length of the are to be welded and an inch or so wider on both sides. Weld one end to the work. Now, clamp the backing plate to your work under the gap. Multiple passes are crucial here. If trhe gap is wider than the puddle that you can create on a flat piece of steel, dont ever try this it will not work to your favor. Lay a root weld to attach both pieces of metal. Remember, the aluminum or brass will not stick to the steel. IF it does. It will release easily. Use the same technique as I explained earlier for making multiple passes. Oh, to prevent this...measure twice, cut once.

Welding in a circle....

Start by chamfering the tubing. Make sure your piece is in the correct spot and tack it in place. Make sure the piece is square and then start your weld. If you cant get all the way around in one pass, get as much as you can. Re position and then start your arc a little bit back on the previous weld and then continue. Do this as many times as you would like.

I may add to this in the future...make suggestions, ask questions!

Last edited by Phildo; 12-17-2007 at 11:40 PM.. Reason: fixed typo
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Old 12-17-2007, 05:49 AM   #2
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Not even kidding, this is the most useful thing i've read/heard for welding sheetmetal. After reading this, I actually feel that I could go bust out a shave job on my truck!

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backer, gas, gmaw, rust, sheet metal, square, weld, welding, wire, wire feed

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