It is like a big pop rivet but with a threaded core. They look good, but would need to buy the tool and the nuts. I think I will use a small hole cutter and then weld my captive nut to the rear of a large flange washer and then weld that washer into the same diameter hole that I will cut. Then at least it should fit and be a rigid section.
The rivnut would not work in this case as there is no real hole, it is split metal where the original nut has tried to pull through.
Anonymous