First Patch MIG project tips? - Vintage Mustang Forums

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post #1 of 21 (permalink) Old 05-19-2017, 12:31 AM Thread Starter
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First Patch MIG project tips?

Did a little practice tonight welding behind the headlight where no can see my goofs. Used the auto setting on the Miller and had some troubles with burn through. Welds seem a bit tall - had trouble getting a good ground.

Do I finish grinding off the bumps and fill in any missed spots?

Any tips appreciated.

Rodney



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post #2 of 21 (permalink) Old 05-19-2017, 01:23 AM
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I'm no expert, but I'd grind and fill with additional weld. Just a minor tip, in general I'd do a little grinding in between the welds so that you're not welding on top of the higher welds. As you get more experience this will not be needed.

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post #3 of 21 (permalink) Old 05-19-2017, 06:42 AM
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Turn up the power. Your weld is too cold. Throttle back the feed a hair, too.
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post #4 of 21 (permalink) Old 05-19-2017, 07:05 AM
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The biggest thing with welding, besides the input already given is prep & clean surfaces properly. You really want bare "clean" metal on not only your new patch but also your piece your patching. I typically take a 90 degree die grinder with a 2" sanding disc and bring all the metal about 1-1-/2" from my patch area down to bare metal, then I take a degreaser like goof-off or lacquer thinner and wipe down the pieces.

Wiping down the pieces is probably a little anal but I have had situations where oily residue or rust proofing left in the area from grinding seeps into the weld as the metal is heated and then the weld is crappy looking.

The other tip is to make sure where your connecting your ground from the welder to be sure that is down to bare metal too.

Over the years I found the better the metal prep (as well as good welder settings) the easier / better looking the final weld will be. This makes final grinding / cleanup so much easier too.

Good luck, you're off to a good start.
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post #5 of 21 (permalink) Old 05-19-2017, 07:27 AM
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I must say that your welds look better than mine. I wish that I had an expert around to tell me when and where I go wrong.
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post #6 of 21 (permalink) Old 05-19-2017, 08:00 AM
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On thin rusty metal, I find the need to stop and let the metal cool for 1-3 seconds regularly. Just so the red cools to metal color then continue. You get a feel for when because the microsecond after you should have stopped it burns through the metal. That is how I get enough penetration without blowing through. On thin pieces that will show, I will do 1 inch long welds and skip around to spread the heat which helps on burn through and is supposed to help with warping the peices. Also, start your welds on the thicker metal and them pull the pool to the thinner arcing back and forth across the gap. Its truly an art I have yet to really master. As 2nd66 calls me, I am a grinder, not a welder...
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post #7 of 21 (permalink) Old 05-19-2017, 08:40 AM
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^^ all good info^^
As far as the second part, there's really no need to weld the full perimeter on a patch that isn't a structural piece, or like yours that's hidden anyway. You simply need to plug the hole in that location, so tack the piece in place- you could leave a little space between each tack, then go over both sides with seam sealer and call it done. Were it a floor pan, quarter panel, etc, you'd want to weld it solidly by doing a short strip at a time and jumping around to avoid heat and warping. 22GT hit the nail- too high = too cold, needs more juice. Something you might try to do is grab a thick longer piece of steel, grind it off clean, and start laying beads of weld in straight rows. You want a nice smooth bacon sizzle noise, not splatter, and clean beads- not bird dookey. Sounds like you just need to play with it, get some time and experience under your belt. I'm sure it'll come to you easily.

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post #8 of 21 (permalink) Old 05-19-2017, 09:31 AM
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Being far from an expert, here are a few things I have found.

Pay close attention to the angle on your tip. If making a continuous bead I like to angle it along the path of the weld, either in a drag or push. BUT for welding in patches in body panels, I like to angle it ACROSS the joint. This lets the arc start on one side and as the wire feeds, it bridges the gap, lessening the chance of burn through. I find I can run a little hotter that way when I need too.

As has been pointed out, do a little grinding along the way. I like to skip all around, then grind the tops off, then make another round, filling in the gaps.

Check the alignment along the way, If you are getting one side of the other starting to pull high or low, it is MUCH easier to do a little mallet or planish hammering before you have it all connected.

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post #9 of 21 (permalink) Old 05-19-2017, 10:20 AM
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A copper backing behind where you're welding can also help. I have a spare piece of copper sheet in my garage, so I typically just cut pieces off that and bend and hammer it so it's 2 ply thick. Then I will clamp that on the backside. It helps absorb heat and can prevent blow-through (unless you weld too long or too hot). Plus if I do burn through, it stop the weld from blowing out the other side.

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post #10 of 21 (permalink) Old 05-19-2017, 10:52 AM
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I'll add to the madness.

First, for sheet metal welding, doesn't look bad. When doing welding of this nature, it will necessarily look like chicken doodle. That''s the nature of the beast when it comes to minimizing warpage (which is a bigger deal when you graduate to cosmetic panels.)

All good advice here. at the end of the day....practice wins!

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post #11 of 21 (permalink) Old 05-19-2017, 10:59 AM
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Is this welded over the metal underneath, or butt welded?

I'm not a fan of overlapping patches, it provides a place for humidity/moisture to get trapped and just rust out again.

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post #12 of 21 (permalink) Old 05-19-2017, 12:48 PM Thread Starter
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Thanks for the tips everyone. It was fun to use the new welder in the car instead of just scraps of sheet metal. I'm going to grind a bit and then fix any holes.

It is butt welded.

I was grinding with a flap disk, worked
OK but wore out the disk pretty quickly. I bought a hard grinding disk this morning. The inside of the headlight bucket won't be a work of art unless I can fit the grinder inside.

I am going to try and make it neat just for the practice before I tackle fixing the holes in the tail light panel.
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post #13 of 21 (permalink) Old 05-19-2017, 01:15 PM
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Are you using .030 wire? You'll get better results with .023 for thin sheet metal. I've a Miller 211 and found when using auto set for .030 I'll get a lot more burn thru. Switching to .023 has stopped most of the burn thru problem. I use .023 for everything until I get into 3/16 or up. Cleanliness is a must, metal must be clean at the weld joint. You need to move around as you weld and allow welds to cool, it'll help prevent burn thru and warping. You can stitch a weld on sheet metal, but usually it warps quite a bit. Then it's hammer and dolly time.
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post #14 of 21 (permalink) Old 05-19-2017, 02:17 PM
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Quote:
Originally Posted by Rodney001 View Post
Thanks for the tips everyone. It was fun to use the new welder in the car instead of just scraps of sheet metal. I'm going to grind a bit and then fix any holes.

It is butt welded.

I was grinding with a flap disk, worked
OK but wore out the disk pretty quickly. I bought a hard grinding disk this morning. The inside of the headlight bucket won't be a work of art unless I can fit the grinder inside.

I am going to try and make it neat just for the practice before I tackle fixing the holes in the tail light panel.
Careful with the hard disc, you can grind more than you want. I use a small cutoff wheel to work down the welds themselves and then the flap to blend it all out.
I usually buy bulks of 3 inch and 4 1/2 in cutoffs, keep multiple flap disks on hand and go through a lot of them. They each have their places.

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post #15 of 21 (permalink) Old 05-19-2017, 03:00 PM
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I use the thin .035" 3 In. discs for actual cutting, and 3/32" to 1/8" wide discs for grinding. With the thinnest disc it's too easy to gouge the metal, instead of leveling it. I do 90+ % of the leveling with the hard disc, as far as you can go without hitting the base metal on either side, and a 3" sanding disc for the final bit. Not a fan of flap discs for sheet metal, they flex too much, thinning the metal around the repair.

Also, MIG welds start out cold, so for tack welds I go up one heat range if the gap is fairly tight.

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Last edited by stephen_wilson; 05-19-2017 at 03:07 PM.
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