In an effort to learn how the more experienced and professional welders handle this, I have a question.

I will be adding 1/8 inch steel to a 356 chassis.
This will be a structural element and will be under some stress.
It is part of the rear suspension.

What is the best welding technique to use to weld 1/8 inch steel angle iron to a standard 19 gauge 50 year old chassis and ensure that the welds hold...they do what they are supposed to and I dont spend the entire time blowing through the 19 gauge steel?
I will be getting the piece of steel from a steel yard, basically a 4 inch by 4 inch angle iron piece welded along the ends, and along the length as needed.

I have a mig welder and a oxy/ace torch.
I dont have a tig, and I wont outsource this...so I am looking for techniques to use what I have.

Rich

I'm guessing you typo'd and meant to say you don't have a tig?

Practicing with the same two gauges of metal is the best thing you can do. Be sure to record the settings you use on your welder, and do a little practice every time you go to weld.

Mig it. Start the weld on the 1/8 and melt that onto the sheet. It takes a few tries to get the hang, but if you watch the puddle you will pick it up quickly. Also do several tacks spaced apart to get the strength there before trying to run a bead like this. That will reduce the chances of blow through and warp

cool, that is what I figured...not sure about the settings but I will mess around with some scrap first.

Rich

Email me photos of what your doing if you want. Maybe I can help. I have never found the need to add heavy metal to sheet steel. You end up relying on the weld metal along the edge of the pieces for strength. Most of the patch work I've seen like this are weaker than if it was done with 19 ga to 19 ga. If you need strength (tosional or longitudinal) use 18 ga. and form it with bends or shapes like the factory did. Otherwise use 16 ga. will be fine(1/16") and use a plug welding method. This will span the overlap on the 19ga and get a better strength.

Rick, I think he's building an outlaw 356 with 911 suspension. Not sure yet, he doesn't want to be treated like an ugly stepchild so he won't talk too much. Some weird welding will be necessary.
When I weld thick to thin, for roll cage bases for instance, I chamfer the edge of the thick metal at 45 degrees and spend about 75% of the time, maybe more, with the arc on the thick metal. I'm talking about mig of course. I start on the thick, keep my puddle on there through most of my back & forth and just give a little dip at the end out onto the thin stuff. Get everything as clean and rust free as possible. Get some extra metal so you can practice on the bench and set your welder before you start blowing holes in the car. Of course I've never blown holes in sheet metal when welding but I've heard about it. Nope, not me...

Me and Rich are twin sons from different mothers. I'm totally into his projects as he is into mine. He knows alot of stuff about what I'm up to that no one else does. I am just pointing out there is a big difference in attaching a stress plate for a cage and attaching one unit body chassis to another body. The factory uses sheet metal. With the right forethought there will be no need to add heavy metal it will do no good.

Im thinking...I hear ya.

Rich

Ok bro!

I still like the idea of building the entire setup on a bench, in a controled and jigged up fashion, then put it in.

I may do that and just bolt it in...that may be another solution.
It will never have a back seat anyways...so I can do this.

I finally got it up 3 feet in the air on a portable table...
Now I can sit under there and work on the back end.


Rich

Lets see some pics of what your doing. I don't particularly like using such dissimilar sized metals on a chassis unless it is in compression or something like that. Think roll cage attachment points. FOr other reinforcements you are better off with something like 18 or 16ga, sheet. It forms better and it welds easier. Plus the extra metal really isn't gaining you anything beyond weight. Proper engineering can help save weight and give more strength.

However you can join the materials you propose pretty easy. I would use a .023 wire and you can run the machine around 5 on the voltage and 3 or so on the wire speed. You will have to play with it to feed just the right amount of wire and not bunch up or short circuit. Always start your welds on the thicker metal and "wash" the puddle down onto the thinner chassis metal. You should not fully seam weld that piece to the sheetmetal, it will create a possible tear point in the HAZ. Also round the corners and edges on the .125 to keep the potential for the part tearing through.

Everything suggested so far sounds good. I don't remember ever seeing any 1/8 4.0 angle though. You might get some sheetmetal shop to make it. All the 4.0 angle I've seen was at least 3/16 or thicker.