Originally Posted By: Slab Happy
Why is nobody listening to Mike H?
using a hole-type drill bit will remove the roofing and leave the spot weld to be ground off easily with the roofing out of the way.

It's a good idea....used in auto bodywork, etc.

These aren't garden variety spot welds though....they're puddle welds.
And they aren't normal puddle welds.
They used cut washers for more purchase and they puddled the ID.

Sounds like a pretty good wart.

It's coarse work...I think that the easiest way to get the roofing off is to cut the roofing around the washers.
Peanut grinder and cut-off disk would be my weapon of choice as I understand the site conditions.

Same concept as a spot weld cutter but rougher.

On the re-roof you would try to lay out the panels so the "high flutes" land on the old puddle welds taking them out of play.
From below the old puddle welds would not show.
Gotta cheat every chance you get.
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NO STEP ON SNEK