Patch panel welding advice needed

[rgunlock]

I've been struggling for some time now to get patch panels welded in where I'm happy with the result. Not there yet. I think I did ok shaping the patch and getting it started. Fits pretty well and is going in flush. I'm taking my time and trying not to do too many welds at once to let the metal cool. This is actually one of my better patch jobs as I only have holes blown out around a couple of welds, and most welds straddle the crack.

This is where I usually get into trouble. After grinding most of the welds down, I try to put welds wherever there is a tiny hole or I see light through the crack. I generally end up with more burned out holes. Do you guys try to cover the entire edge of the patch with welds? Do you leave it more like in the 2nd picture and figure the seam sealer or filler will deal with the tiny spaces and holes? Looking for advice before I screw up this little project. Thanks!

[Bomp]

Personally I try and weld 100%. I admit its not necessary for body work but I'm not a pro.

On my build i have pics of welding on sheet metal and frame section areas. Along with video.
Looks like you have a good grasp on what your doing, time working on patches will help in the future.
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[rgunlock]

Thanks Bomp! Got a kick out of your welding 101 video

Going to have to go back later when I have more time and check out the rest of your thread - looks like a looonnnnggggg read!

[Bomp]

Its a build that kinda spiraled out of control.
One thing though I'm not taking any short cuts and have not set a finish date cause ........well I'm not going to hurry.
Enjoy the read and feel free to pm me if you have questions.
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[_Ogre]

your burning thru the base metal because it is thin from rust
even if you get the metal to fill it will be very thin and rust out if the back side is exposed to water

a couple of choices:
cut out more metal until you get to thicker material
cover it with a layer of short strand filler like duraglass
backer material to suck up the heat

i'd get it to the second pic and cover it with duraglass
duraglass is waterproof vs regular filler will pass moisture thru

[rgunlock]

Thanks for the advice Ogre! I think I have a multipart problem and you've hit on part of it. In this particular patch, I should have cut out more metal where it bends over at 90 degrees. Didn't realize how thin that was. I think my other problem is I tend to get too aggressive grinding the welds and make the metal thin so I get burnout when I try to touch up.

I have gone back and put in more welds to get to the point I only see a couple pinholes along the edges now. If I can get this ground down without making a mess of it, I think I'll leave it at that point and try your duraglass suggestion to finish it off.

[mr48chev]

Ogre pretty well nailed it, you have to cut enough out to get out to good metal that isn't partially rusted away. Sometimes that makes for a bigger patch than we want but the end product turns out better. I really haven't mig welded much sheet metal as in the past I've always gas welded it and even then I blew some holes in thin spots.

[rgunlock]

Well, finished 2nd round of welds. Was looking pretty good after grinding except one spot at the top of the weld. Went to touch it up and blew out a big hole. Filled it using copper backer, but you can see what a gob there is on the backside of the patch in 3rd pic. I think that I'll be cutting this patch out and re-patching a larger space as you guys have suggested.

I think I'll sleep on that for a bit though. This patch is the underside of the cab and maybe I'll decide this is good enough to cover up with undercoat

[dwcsr]

One thing you can try it to start the arc on the edge of the last spot you did. If you start on a bit of the last spot you have much thicker metal to weld on and less chance of burn through.

Start with the recommended setting on the welder
Try turning down the heat a little until it looks ok and still penetrates ok.
Make sure you're not too fast on the wire speed. That will force a hole when it goes red

This is a good video on setting up for a particular metal thickness

Welding Tips: How To Set Any MIG Welder Video...

or

Tuning A Mig Welder - YouTube

Setting up the mig is key to good panel welding

[rgunlock]

Very useful videos. I did go with the recommended settings listed in the welder cover, but didn't do any of those tuning steps. Something to try on my next attempt. Thanks Dave!