Starrett KD0158-N 1.5/8-Inch Diamond Grit Holesaw Effective cutting of hardened steels, fired ceramics, aggregate containing concrete, non-metallics and other difficult to cut materials Clean effective cuts and extended life Uniform synthetic diamond grit bonded over a durable steel platform Always use a coolant and start at a low speed, increase speed as ease of cutting is noticed while avoiding heat build-up on the cutting surface Recommended cutting speed is from 150 to 300-RPM