Improvised slide hammer 'welded' to dent in car's floor

I think it's much more likely that you will simply burn a hole in the floorpan, it's very difficult to arc weld thin steel.

I think you'd be better off screwing a plate to the floorpan with several self tapping screws and attaching the slide hammer to that in some way.

Also, does it matter? Can't you attack it from the other side?

Where should we send the flowers after the explosion? Brian

No, it's a blind void. And I'm *not* trying to arc weld it to the floorpan like the other fellah said. I'm planning to jab the shaft up against the car chassis while it's hooked up to the welding transformer in the hope that they fuse together under the heavy current. There is a variation of this technique in common practice in pro body shops. Here's how it works in principle:

Very droll I'm sure. I'll be using a proper industrial Oxford oil-cooled arc welder circa 1973 for this job, not some crappy Chinese "turbo" fan-cooled, low-duty-cycle job, so there won't be any explosions.

Well it might work although stud welders and spot welders usually rely on an adjustable timer (or fixed timer and adjustable current). And you saw how clean the body shop guy got the surface. But I still wonder why you feel the need to fix it if it is only protruding into a blind void.

Fair point. If you could see it, you would notice it's torn away the jacking point from the surrounding metal so there's a fissure you can trace your fingernail though. This is an old classic so the metal is not as pliable as a new car would be. By the same token, some rusty holes have opened up on the other side which had it been undamaged, would not have been apparent. Need to fix these issues, not just for the sake of completeness, but my conscience! I can get the area clean no problem, but am inclined to leave it be as a little resistance would be no bad thing, since it generates a hot-spot when high current is passed through it, which is in this instance at least, desirable!

I know nothing about these things, but the weld has to be strong enough to take the hammering, so how do you remove it later?

Dent pulling for thin body panels uses hot melt glue and attachments to the slide hammer with different surface areas. Sprayed IPA will release the glue from the panel. I've got very limited experience of this technique and it is not just pulling out a dent but also knocking back high points (ridge lines etc.). In the OP case cosmetic perfection may not be required on the underside of a car.

I disagree. You will get the peak current density at the contact from the constriction resistance effect. You do *not* want to include oxide in the weld, because this will reduce its strength.

I've seen glued ones & spot welded ones

Or multi-tool with metal-cutting blade fitted.

Can't you just cut the whole shebang out and weld a new bit in like they have done for generations before this dent pulling carry on

Which decade of late 19thC are you referring to? Light dents, fair enough. Trouble is, some dents are bad enough to draw in the surrounding metal and depending on where this happens, the only remedy is to fully restore the correct geometry around the affected area, which can only be achieved by pulling whilst tapping down the resulting 'caldera' with a metal shrinking hammer.

Angle grinder

Angle grinder

...& large stack of "metal cutting blades"...