[Flathead Fever]

My dad worked out at Kaiser Steel, a WWII steel making plant. He taught me how to take rivets out. Grind the rivet head down until its turning red. That's when the head is just paper thin, stop grinding before your grinder breaks through it and touches the frame rail. Then center punch the rivet and drill it but do not drill all the way through it, just enough for the bit to make it through frame rail. Drill out most of the rivet but do not use a bit big enough to accidently drill into the frame. When the factory rivetted them together the rivet was red hot and expanded into the hole tight. You need to relieve that expansion by drilling the rivet but without hitting the frame rail. Use a bit a couple sizes smaller than the rivet, maybe a 1/8" smaller than the rivet. Since you did not drill through the rivet all the way it's left you something for a punch to rest on, a couple strikes of a hammer, and it will pop out and leave a pristine unmolested frame hole. I Hate Butchered Torched Rivet Holes, there is no reason for it.