mig welding in patches

[tinlizzy]

I have a 48 pilot house that has front fender ills.

Pop rivets have rusted out and several places have cracked edges.

I splurged and bought a new mig welder. I have had advice from several people but it is not working. I tried experimenting on old pieces before working on the fenders but welder just seems to burn through the sheet metal.

I can't seem to get the sizzle noise I need to know I have the welder set right. The area has been ground clean where I need to make the patch but just can't seem to make it work without making a bigger hole than I have. I am using .30 flux wire, the voltage is set at lowest point and wire feed is set at just the point where it don't push when I press the trigger.

Help what am I doing wrong?

Lee

Edited April 11, 2010 by tinlizzy

[mikesinky]

i aint no expert welder or nothing but i have done plenty of it. when your burning through you usually either have your welder set too high or your going too slow. you said your welder is at its lowest setting so probably not that. so here is how i do it. just spot weld when its thin. dont try to do a whole line unless its laying down good without burn through. if it burns through stop. let it cool to where it aint glowing red and just spot it just hit the trigger and quit. dont start at one end and try to go all the way around. first tack all the way around start on the corners to make sure it doesnt warp. then just spot some tacks all around. weld on say one corner for a little bit then switch to another corner and just keep welding a little bit at a time. and make sure your nozzle isnt too far away from your work or too close keep it about 3/4 to an inch away. and lots of practice you will be surprised you will keep screwing up and then all the sudden bam it will come too you like you were doing it for years. i hope this helps. you might even get some smaller wire but .030 should work.

[Plymouthy Adams]

welding thin or "thinning" sheetmetal that has ben subject to previous rust and then derusting techniques can make using a mig a nightmare. The heat and speed has to be varied as you move about the weld area and your inability to see the quick change of these properties causes you to push righ on through. Mig is at best good for continious run on exact thickeness clean metal. I recommend using oxy/acetyle but then you may not have access to that. A technique used for weld run starts is to clamp a good metal tab in front of your weld to get a good burn (sizzle) before advancing onto the area to be welded. Mig also leaves a hardened metal behind (brittling) instead of a softer more malleable metal left with the torch..

In using a neutral flame in flame (blue in blue) torch you can see as you weld instant heat changes and thus prevent the burn out..should you burn out..no biggy..continue your bead..come back and puddle in the hole..quick and easy..do use a 00 size tip with approx 6/12 gas/oxy pressure..even less if you have the Henrob 2000

last item of concern..is your mig of high enough quality to allow proper heat and wire feed rate for you to do the work you are attempting..some lower price units can be a bear to set up.

[austinsailor]

Try just making many tiny spots. I go along and just tap the trigger, making just a tiny spot. "Stitching" is a term I've heard for this. In fact, I saw a video some years ago of a welder that had a setting for this. You pulled the trigger, and it would just do a fraction of a second "sap" wait "zap" and so on. I don't have a machine like that, but use my trigger finger to do the same thing. Just barely enough to make a tiny puddle, then wait. You can keep the metal red, but not melting it except that one spot where the wire hits.

I've taken pretty rusted, thin jagged spots, gone all around the thin area around the hole like that. It'll melt back just a little until you get a thicker edge built up, but eventually it'll make a solid enough edge to work too. I seldom use the trigger on continously. Lots and lots of little spots.

You can actually weld on the edge of a piece of sheet metal and build up and replace some missing metal this way. Of course, you'll have to grind it some to make it smooth.

I use a welder with gas, not the flux core, it might not work quite as well with flux core.

[JBNeal]

I've done stick welding on sheet metal, with the electrode as the negative & ground as positive, following a method I read in an old welder's book. The trick is to stitch the weld to keep from burning through the base metals. Some older body work I've found appears to be done with oxy-acetyl, either done well or done marginally, but either way the base metals did not appear to have distorted or burned through.

[Jim Gaspard]

Tinlizzie, I have had an identical experience. I picked up a Hobart Handler 125 gas-less Mig at a swap meet to play with. My first attempts with .031 flux-core on the slowest setting turned out the same way. Holes got bigger not smaller particularly with rusty areas. I ended up flooding the area in spots, then grinding down and repeating. Finally got 98% coverage and epoxied the rest. Getting better at it, just takes time and getting the feel of the welder. I've seen the sister Hobart model weld but with the argon gas supplement and the flows seem much smoother. That will be my next purchase as I perfect my techniques.

[tinlizzy]

I bought a Northern tool 140 with gas option, looks just like the Hobart. I didn't want to spend a whole lot for first time out but it was still almost $400 with the extras. I tried just hitting switch to make a tac but just blows through no matter how quick it goes or all I end up with is a bee, bee size spot that hasn't stuck to anything. The metal seems to be solid enough that it shouldn't go through that easy but it doesn't seem to stick.

We have a certified welder where I work, I think I will take it in next week and let him show me what I am doing wrong. I know this isn't brain surgery but either I am not doing something right or I am not set up right. I was able to run a nice bead on heavier stock metal. I am working on the rivets on the front fenders. I also have a couple of places on cab bottom as well as floor panels that will need repairs and the rear fender bottoms.

My door bottoms will also need to be fabricated as they have gone bye, bye.

Thanks for the help.

[48Dodger]

Fluxcore wire tends to be more aggressive than wire with a gas shield at the same setting. If you're going to spotweld with the fluxcore, point the nozzle down the bodyline to "thicken up" your surface. Clean the spot weld of the flux/slag (wire brush) between multiple start/stops.

Got pictures?

48D

[Dodgeb4ya]

The use of a copper backer bar held tight against the joint helps big time. Flux core wire is not the way to go either. Use of C25 gas /solid wire is your best bet-if your machine uses gas. Gas welding is the better way on a lot of sheet metal pin hole jobs as Tim said. I'm in the middle of one of these jobs on a 50 Chrysler right now.

Edited April 11, 2010 by Dodgeb4ya

[tinlizzy]

No pics, I guess I need a digital camera too. Don't think mama would be happy if I spent an additional amount for a camera too.

[Dave72dt]

Get rid of the flux core and get the gas hooked up. Every time you pull the trigger on the flux core it'll leave a residue on the metal that needs to be cleaned off before starting another spot. .030 wire will burn hotter than .023 so pull the .030 wire out as well. Spot welds only on patch pieces spaced an inch to 20 inches apart. I do two or three spots max in any one spot before moving on to another cold spot. Limit heat buidup to the point where you uncomfortable laying your hand on it. Check your work often for fit and shrinkage/warpage. Whe n yopu get some, however slight, work it out at that point. Do not continue welding unitl it's worked out, you'll only make it more difficult later. There should be a setting chart somewhere on the welder that should give you some base settings.