Recently I made an error and needed to drill several AN470AD4 rivets in a very confined space. All went well, first drilling the rivet with a #40 bit, then drilling through the head with #30. Most of the heads snapped off clean by using an old drill bit, but one or two refused to break clean. I didn’t want to do damage to the part by forcing the issue, so a new tool was born.
I’ve used chisels before for all sorts of jobs, and this seemed a good fit. Plus I like homemade tools. I took an old butterfly wood bit and clamped it in the vise with the point protruding above the jaws. One good whack with a hammer and the point was removed.
Next the end of the bit was ground to an angle with a sharp edge. I finished it off by removing the sharp corners and all but the center 1/4-inch of the edge.
Back to the stubborn rivet head. Position the chisel at the edge of the factory head with the sharp edge against the part and as close to flat against the part as possible. One sharp tap with a small hammer dispatches the head with nary a scratch on the part.
I also sheared off a few shop heads of practice parts; it works well, but be very careful. The sharp edge can dig into the part if the chisel is not held very close to flat against the part.