Originally Posted by Aerowood
The best drill bits to use are 135 degree split tip in cobalt at around 3000 rpm, more expensive be last 10X longer.
Many years ago, I found these for sale in solid carbide, double ended (I think at the EAA airshow back when it was still in Rockford, IL.) ... in a SHORT version - perhaps two inches long. They are terrific, if you can find them - because of their short length and hardness, they don't flex or wander at all, and they have lasted for literally decades and have drilled zillions of rivets and rivet holes. Also, because of their sharpness, and when used at highe speeds, they cut fast and clean. Chuck up one of these in a high speed air drill, and yer' ready to go!
Only drawback is that you need a diamond wheel to sharpen them. Then again, I've never needed to sharpen them!