Mark from work got this flange rewelded on. It came out quite well.

I knew from reading Jamie Painter's site that I would probably need to trim the weldment to allow clearance for the shop head of this rivet. I stuck a punch through the hole and whacked it a couple times with the hammer...

...so it would create a mark to indicate where I needed to trim.

A short while later and the die grinder made this nice, radiused clearance notch.

You can see there's plenty of clearance for the shop head of that rivet, now.