I have done many good welds on this 18 gauge but there is a small tear in one door that I worked flat and welded up but ever time I grind it down with the 36 grit wheel I see one or 2 pinholes. I know I am hot enough, it is melting in well and any more heat and I burn through, what gives? any ideas? I am about ready to everglass over it and move on but I guess I am a stuborn perfectionist. smile.gif

zach,

Sometimes there is slag in the weld, This will not let the hot metal stick, Drill out the hole put a piece of copper behind it and weld it up, Use a 1/8 or so copper and make sure it's flat. Hope it helps,,

what is the purpose for the copper? so it doesnt burn through? or so the weld dont fall through the other side.

aaron

Zach, when I first welded in my rear guarter skins I stood back and admired my work. I then put a light in the trunk and turned off the lights in the garage. :eek:
It looked like a street lights lining a highway as seen from a plane :D
Thats how I ended up finding all the holes and going back to fix

Originally posted by BowtieAaron:
what is the purpose for the copper? so it doesnt burn through? or so the weld dont fall through the other side.

aaron I use an old brass car stereo distibution block to back up some spots I'm welding to keep from blowing through. The weld does not stick to the brass HOWEVER if you are welding a lot it transfers the heat VERY, VERY well and I have to let it cool or grip in in some pliers to keep from burning myself.
I have also used some small strips of brass to back up other areas when welding like on edge of a door or fender to tighten up a gap or to make the gap more even. I used the bigger block when I was welding in a seam on a large patch in my hatchback floor and I had over trimmed a few spots by rushing the fitting of it and I was left with a larger gap in some spots between the edge of the old floor and the patch. By backing it up with the block it was easier to butt weld the two parts together.
If you do get pin holes after welding a spot and grinding it down ideally you need to add some more weld and grind those down until there are no more holes.
Jim

Thanks rags I will give it a shot. I did notice that welding up some 5/16" holes from old mirrors was easy and it had no pin holes with no backup.

I use a piece of copper( or should I say my helperie.. my dad) that has a handle on it Eastwood sells it for $20 it is called the welders helper and it works great!!! ;) I just clean it with a roloc red pad every so often, it is great for butts that have too big a gap.

Just speaking for myself, my welds improved tremendously when I bought a pair of 2X magnifiers, I realized I was just pushing sparks around until I could actually see ( DUH! ) the pooling and I got a pin-hole free weld AWESOME!!!!!Ps maybe those of us over 40 or 50 can appreciate this post

Some pin holes are caused by too much heat. I do the same things at times and it is a hard habit to break.

When I look at the back side of a butt weld I want to make sure both sides are "melted in" and that you can't see the straight lines anymore right? If not it needs more heat?

Just cerous how long of a bead do you guys run on 18 guage butts? I run a 1/2 to 1 inch and let it cool to finger touch before laying another next to it.(ie.. I move to a different place and lay another bead)
I tried that just tack the whole pannel in in different spots, and it took for ever and a day! My welding instructor told me to weld about a inch then stop and start a inch away from the end of my last bead and weld back to it.

You don't run a bead, sheet and thin should be stitch welded. Stitch welding is just a small tack weld to prevent warping. See MartinSR posts on welding.