[PIF]

There is a difference in the drill marks left by a low speed and a high speed drill going through a given material - If that isn’t enough ... many have tried to duplicate the results with both methods of ancient drill holes and the high speed won in the cases claimed.

If you can’t figure the truism out then that’s your problem.

[GingisK]

I use drills quite often in my machine shop. Depending on the material and the bit, one cannot reliably tell the speed of the drill. Feed rate is also a factor which confuses RPM considerations.

Bow drill can turn rather fast.

No, I can't read your mind. Thanks for the deflection from the brotherly bonds of Free Republic members.