Miller Electric

Welding Discussion Forums

Home » Resources » Communities » Welding Discussion Forums
Miller Welding Discussion Forums - Powered by vBulletin

Results 1 to 7 of 7
  1. #1

    Default tips for welding thin gauge sheetmetal

    Hi guys! I am getting ready to do alot of welding on thin gauge sheetmetal. Mainly 18g and 20g. Any tips for welding it up without warping the metal. What about having a damp cloth that you tack and cool? Is there any kind of heat absorbing pastes that i could put on the metal? Anything will help.

    Dynasty 200dx
    CoolMate 3
    Millermatic 180

  2. #2
    Join Date
    Dec 2008
    west central Florida


    Quote Originally Posted by abadsvt View Post
    Is there any kind of heat absorbing pastes that i could put on the metal? Anything will help.

    Copper and aluminum make good heatsinks.

  3. #3


    Warpage is the nature of the beast; it's going to happen.

    You didn't state what process your are using; MIG, TIG, OA? Also didn't state what you are working on? (I assume autobody work...)

    Heatsinks don't really help at all. The warpage problem comes mainly within the HAZ, which you cannot heatsink away.

    Best option is to plan for the warping, and fit things up good. First tack your entire welded area; that is, tack in all spots to hold things in place. Then use short "stitch" welds to grow the tacks. Limit your heat input; short stitches around the periphery. If you are using OA, hammer-welding is best; (weld a short stitch, then beat on the weld backed with dolly while it cools to keep from shrinking.)

  4. #4
    Join Date
    Jan 2009


    tacking it alot helps the most, thats what i do when I tig weld duct work

  5. #5
    Join Date
    Mar 2009
    Corona, CA


    Best things I have for working with sheet metal that thin, is move fast when you're welding (obviously don't make it crappy just for the sake of speed...), and let it cool down between welds/tacks.

    I always keep an air hose near by and when i finish a spot, blow it down real quick. If youre moving around a larger part, that can keep you from baking yourself to your project as well...

    Good luck to you!

    By far though, OA or Tig would be the easiest to hammer/dolly if it needs to be perfectly straight when youre done. Mig welds tend to crack more than flatten.

  6. #6


    Here's another point I forgot. If you are TIG welding it, then try to get your materials to fit perfectly; no gaps anywhere. Be real cautious tacking; when it fits perfectly, it will be hard to tack without it moving on you. I've often tacked a spot, then hammer it to keep the part in position exactly, moving onward the same way.

    Then if there is no gaps anywhere, try to weld with as tiny of a bead as you can, with little or no filler, rapidly, with the stitch method mentioned above.

    I've had good luck with this method where I could not easily hammer weld the whole patch.

    I don't MIG thin patches anymore due to the reason stated above; the bead is too hard and prone to cracking when you try to straighten it out later. I still use the MIG on body patches where I plug weld them at a lip (poor man's spot weld...)

  7. #7


    I have gone down this road. I am not an expert or even close to being a competent welder, but I just finished successfully MIG welding a bunch of 22 gauge old and new sheetmetal. I only have a 115V Lincoln ProMig 140 and ran 0.023 w/ C25 w/ machine @ "B-5" voltage / WFS.

    I was originally running about 1/2 to 1inch of weld bead, but getting warpage. The guys on this forum suggested to do the tack welds. So I tacked every 4 inches, then came back and added ONLY tack welds adjacent to the first pass. Continued that process until they were connected up. I got MINIMAL warpage on the welding passes. I did screw up grinding and got too much heat in a spot, but at the time I was using an 80 grit flap wheel. That was a mistake. Switched over to a hard grinding wheel and cleaned up the welds w/o spending too much time in one spot. Finished up w/ 80grit on a DA.... Smooth as silk. I tried cooling the welds w/ a wet rag, but that was a mistake - I just let them air quench. If you're working a decent sized piece, you can make a round of tacks and the first will cool itself by the time you're ready to make the second round....

    There were a few spots I hit w/ hammer&dolly and a shrinking disk, but not bad....overall very little warpage. So for me, I recommend DO NOT do anything more than tack welds (if MIG) and DO NOT rush the quench process. All that being said - if the guys here say use O/A or TIG, I'd use the O/A or TIG.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts

Warning: Function split() is deprecated in /mnt/stor3-wc1-dfw1/357822/357839/ on line 79

Welding Projects

Special Offers: See the latest Miller deals and promotions.