I found it works the best to grind a flat on the rounded head, center punch and drill a hole slightly smaller than the rivet diameter almost all the way though, then use a drill larger than the rivet diameter to remove the head, followed by a punch to knock the remainder out. Many times the original holes are not lined up and the rivet expands to fill the area when originally bucked. As a result it is easy to damage the frame material if too much brute force is used.
x3 on the above advice.I found it works the best to grind a flat on the rounded head, center punch and drill a hole slightly smaller than the rivet diameter almost all the way though, then use a drill larger than the rivet diameter to remove the head, followed by a punch to knock the remainder out. Many times the original holes are not lined up and the rivet expands to fill the area when originally bucked. As a result it is easy to damage the frame material if too much brute force is used.