Up to 3/8" rivets I use a long 1' cold chisle and as big a hammer as I can swing, makes quick work of them. Much faster than any drilling or grinding method. Easy to punch out the remnants once you cut one head off. Won't hurt the frame any either.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-