[rotorwrench]

I've drilled so many rivet heads and buck tails the I can't even count all the projects any more. Getting centered is the most important thing move the drill to keep it centered if you have to. Use a bit that is the same size as the rivet and have a punch of the same size to break the head or tail off before further drilling if needed. Use an automatic center punch or a punch with light tapping. If the rest won't pop out the drill some more until it does. Try not to drill all the way through unless you have to. Use the best bits you can afford. I use cobalt after the high speed steel ones get too worn down. I learned to sharpen them a long time ago but a bit can only be used till the central spine is too wide which makes further sharpening impossible.

Wallered out rivet holes should be welded up or patched and redrilled. You might think patching is crazy but I'll patch a hole before welding it up in some cases. Making little patches is a pita but some holes are too big to weld up and I don't like using filler rod if I don't have to. I use an aircraft gas torch to do all my sheet metal welding.