I'm replacing the roof skin on my 66SS. I've got the skin in place and I'm ready to start spot/tack welding it into place. On the flanges where the skin meets the subframe, I've used 3M weld thru primer on both the skin & subframe, I have holes drilled in the skin where I will spot weld with my MIG welder. My question is, when I look through these holes, I'm looking at weld thru primer, do I have to remove this to clean metal in these holes, or do I just start welding & burn through the weld thru primer? If I have to clean it, how the hell do I do that? Mini wire wheel?

Just weld right over the weld through primer.

Chuck

As the Can said " WELD THROUGH PRIMER " and thats what you do. Rember slow and easy,
blow it cool with compressed air, to minimize
heat transfer and keep it from warping.
GL

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Wayne
ACES 1556
TCG 186
So many Mustangs
So Little Time

Use a small screw ditver to scratch out the primer just a little to give the welder some metal to start it going easier.

I'll second that, Brenden. I sometimes have trouble striking an arc, especially if I sprayed the weld-thru primer on a little too thickly.

First of all, I don't like 3M weld through, but it's a little late for that. SEM is the best for me.

Don't worry about scratching the primer away. Let it dry GOOD, as it now is and this is the trick...are you ready?......
Have your wire cutters with you and CUT the MIG wire off after EVERY weld. That is all there is to it. I started doing this only about two months ago and I can't believe the difference! The cut wire is sharp and it pierces the primer. I don't remove Ecoat anymore either, just weld right though it. It is high in Zinc just like the weld trough.

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1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T
"Fan of most anything that moves human beings"

[b]Have your wire cutters with you and CUT the MIG wire off after EVERY weld]

I got into the habit of doing this the first day I learned to MIG weld.

MARTINSR, I think I'll be emailing you some pictures of how I laid the skin on along the front edge where the windshield molding goes.

If you recall, the metal on that front spot weld flage was too thin to use, so I'm lapping the new skin to part of the old, I want your opinion befaore I start welding.

Right now, the existing part of the old skin is no more than an "L" shaped flange, I want to know how far down I should cut this. Right now the welds would end up right on the crease, I'm wondering if I should go down farther.

MARTINSR Good idea I'll have to give that a try.