repairing holes that are stretched

[fusername]

So this is more an exercise in theory than application, since by the time I get a response I will have done the repair. I have 5 holes in good sheet metal on my bus from bolts being pulled thru the panel. so the hole is about 9mm wide, and the bolt head got pulled part way thru on all of them so it has a little volcanoe look to it. What would be the right way to flatten these out for a show quality repair? I know if you heat the metal cherry and tap it flat, when it cools it should pull some of the ripples out. Is the trick to back it or not bck it when you hammer it in, and is it one or two good quick whacks, or many small light taps that make the metal do the proper magick that you don't just end out with a fun house mirror?

NOTE: I am not doing a show quality repair, I will spit mIG wire at it till the hole is full, grind it flat and paint and call it good, this is a woods car, but I want to kNOW the right way of doing it, even if I don't do it.

[Piledriver]

Back it and use the shrinking hammer face (Looks like a waffle or framing hammer texture), just as much battering as it needs. hit it too hard it will stretch back out.

The heat/cool bit will get there eventually, if you have infinite patience and get paid by the hour...

[Ol'fogasaurus]

Like Pile said but you can do it with a flat face hammer and dolly too. You want to shrink the metal as Pile said but you need to work the hole from the outside in. Another way I have seen it done, as long as the volcano isn't too big is by using a nut, bolt of a smaller diameter than the hole and two large diameter thick flat washers that are a tight fit on the bolt (one bolt size smaller hole); bolt head on the far side w/one washer and the nut and other washer on the near side then tighten things up. Warning, this doesn't always work so plan a head. You will still need to do some hammer and dolly work to finish off the shape.

I think a slap hammer might be better than a hammer aslo. I had a friend who did metal working and he heat bent an old file to a Zee shape and used it as a slap hammer. It put texture on the metal for Bondo to attach to.

Lee