there is a difference between masonry drill bits and concrete drill bits. Masonry bits have a sharp cutting edge on the carbide tip and concrete drills have a carbide tip that is shaped diffrently for taking the beating from an electropneumatic machine such as a HILTI hammer drill.
Diffrent size bits cut at diffrent speeds. A drill press helps for proper speed and holding bitt straight. Nothing can move or the bitt breaks. about 800 rpm works for most knife making speeds.
This is an impressive amount of information guys. Thanks for helping Gary. Glad you got it done Gary, can we see what you were drilling a hole in?