I have chopped the top on my coupe...first chop...turned out pretty nice. I welded it all back with a mig (no tig available) used .30 ER70S-6 wire a tack at a time moving all over to minimize distortion...I have ground the welds down used flap discs, rolocs etc. I want to use as little filler as possible...I believe I will have to do some hammer & dolly work...the welding has left a low spot....but I am worried the welded area will crack....I know mig welds are harder and should not be hammered .....take a look at the pics and any advice/tips will be much appreciated..... Thanks
you can hammer your welds lightly but if you really work them over you will crack them. looks like you have done a nice job so far. dosent look like you will need much filler anyway. hammer the lows or highs out the best you can. some guys on here use a shrinking disc for your high spots, never used one but looks like it would work well. good ol torch works good too. but i doubt that that will be necessary
Hammer lightly as said. If they crack,go back and re weld a little slower to add more heat. Then re-finish again. Or you can gas weld the cracks if you have a set of torches.
Model a's are fun to chop. Pretty much straight down. Did one including mlgs in 8 hours once on a 2 dr. I gas welded mine at the time so i could hammer weld it but your be fine there.
Take a picture with a straight edge on it.So we can see how much you need to work out. I work mig welds all the time,but I weld a inch stretch the haz then move on.So in that inch it only takes 2 or three light taps.You will have to do a more then that now. You should have cleaned the inside as well.Thats why there is a white ring around your penetration.That is not ideal When I grind welds I use a 1/8th inch cut off wheel to knock the proud down,then I would stretch the haz.Then when I finish cleaning my weld I take the last bit down with a file and then 80 grit sand paper.I try really hard not to take anything out of the sheet metal.I think most cracked mig weld come from people over grinding their welds.Don't get me wrong over hammering on a mig weld will defiantly crack it.That is why you should try to keep up with it as you go. If you want to work it out it will probably take two people,unless you have long arms Clean the weld up some on the inside.I would leave a little meat on the inside weld. Then hold the dolly directly on the weld inside of the car,then hammer lightly on the haz(heat effective zone aka blue area) on the outside of the car.This is called dolly on,dolly on stretches.That is the only area you want to hit because that is the only area that was effected.Feel your progress as you go and be patient. The chop looks good good luck good luck
I don't think a little mud will hurt but in the second picture it looks like its sucked in pretty good. I think he should give it a shot and get it a little closer first.I don't think it will take to much.
jhnarial ....thanks for the advice.....I just found out about that technique of weld 1" and hammer the HAZ, a little while ago....of course after I already welded it up.... Is it worth employing that technique now ??? ...can it be done now ??? can the weld seam be re-heated and hammered ??? So...hammer & dollying the welds or stretching...even after I've ground them down...should bring the sucked in area back out ??? I will post another pic with a straight edge ASAP.
No heating it will just make things worse.Adding heat will shrink it you need to stretch.the metal shrinks when you weld it(that is the blue area around the weld) so if you stretch that you will be right back to where you started from. If it was fitting right before you welded it,just working the haz will pop it right back into place.It will take care of your problem.That is if you do not crack the weld,hit lightly and go slow.Little at a time. If you can go from a 1/4 inch of bondo to just a skim coat,that would be huge. Next time try to keep up with it as you go one inch at a time.It's worth a try anyways.That is the only way a I will weld sheet metal.Doesn't matter mig or tig. A lot of people think,that it takes to long.The way I look at it is,I could have spent the time I loss trying to fix a oil can dent or covering the whole car in bondo. Thats a good looking car
Using a wooden hammer around MIG welds helps some . On mig welding you have to have your panels perfectly aligned , as you dont want to move them around much after the welding starts.
Johnny are you saying you run a 1" bead or do a series of tacks until it is 1" solid? I've always done tacks and spaced them out so I don't overheat the metal and warp it, but my welds usually cave in like that too. I want to learn how to do this technique correctly.
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