Thread: Welding sheet metal

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when you put a patch in you want to get all the rust out i first tap it with a body pick hammer too see how punky it is them cut out with a cut off wheel take bad part off flip over look at the rust on the back side if rust is past your cut take a hammer tap off the rust the part you cut off see how thin the metal is if thin your have to cut bigger repair if you do not do this the patch will fail by the time you grind and prep for paint your fix will be paper thin and any time you weld the metal is now super clean all junk has been boiled out where you welded it now will rust much faster . i was a flat rate body man for many years i have welded many panels on and made many i never used panel bond on any thing other then door skins .for me a butt weld work the best .if i had to a small over lap i never use a flange tool .i some times welded the panel from the back side if i could get in there like if cutting down running boads .on how to weld with out warping. one thing i used thicker sheet metal for the repair .i always welded just under a body line if there was one not to far from the patch like a door bottom or fender . fit up is a big deal . and very clean were you weld. i tack welded the panel down keep going till about every 1inch a part once tack you must not let it get very hot .i set the mig welder for low heat and not alot of bead more bead more grinding = more heat = wraping . i ground the heads off the tacks thru out the tacking job so i can work the steel if needed with a hammer and dolly if a low spot can not be work out cut the tack loose pull up and retack when all tacks are ground level to metal then i move up the tacks till they are less then a 3/4 apart then grind them flat and wire wheel then a go from tacks to welds and only weld about 1/2 to 3/4 between tacks no more .when cool grind weld flat. and hop around never start form one end and stop when done.i walk way till cool s down .it is still to hot if you can not keep your hand on it. get on and off the panel with out putting alot of heat in to it . i set welder or check wire speed for low bead . when the panel at this point it is harder to warp but still can hapen. i let it cool down by it self or a damp rag you have to watch this water or blowing can shrink the spot that can make it wrap to that may not be what you want. i never hit the weld any more then needed with a hammer and dolly this can make stretch the steel so you do not want that. i ether i used a hi speed angle grinder with a sharp 24 grit(new) or a grinding stone you want to get on and off the panel do not dwell on the weld. the way i did it there was not much grinding when done .as i did it along the way.i never used flap wheels they will not cut the hi s off the weld just blend and they make more heat = wraping if you want to seal coat the back side after welding there are things you can buy or make you can use firber glass reisn or a west epoxy put on with a brush then epoxy paint it then use a uncoating work in with a brush or amber wax bass under coating sprayed in with a under coating gun . before you get this far you many want to add a drain hole at the bottom of patch i used the word Tack less then a 5/16 to 3/8 spot weld ideal size was for a tack was 3/16to 1/4 of weld for me

Everyone who says to not run a bead is correct. Hope you are using a mig welder with sheilding gas, so much easier to clean up. A 110 V. with shielded wire is good also, be sure to wear your safety glasses when you hit the slag with your grinder. Skip weld is what you use, and until you are competely tacked up, spot abot 3" apart then "skip" around with 1/2" welds until you get it stitched completely. You can get your metal to pull tight by applying a cool damp cloth immediately after you finish your weld. If you ard using a stick, a cooler weld can be achieved by "pulling" the rod away from the work slightly after you strike your arc. I use that method on 20 gauge and lighter, and hold heat to 2 seconds or less. works well with cold galvenized, too.

I found this website in good old plain english that might be of help to all:www.weldingtipsandtricks.com:)