See now, my theory of operation is just the opposite. Those bits are meant to be run at high RPM. High RPM and little bites, always moving in the same direction as the bit rotation. Sure I slow down but thats when the thing bites and does the wallowing bounce act. I don't have much experience with the long bits or even porting for that matter, but I have put a lot of miles on die grinders working in the collision repair industry. I bet they told you the same thing about grinding on teeth. In the end it's whatever works for you and failure is just another word for experience. Gotta keep a mindful eye on that grip too.
