For rotary drilling only. Includes 5/32 pilot bit which must be used first. Ideal for drilling porcelain tiles up to a scratch hardness of 8. The drill bit will not walk， tape or center punching is no longer needed. Flat bottom parabolic flute ensures fast and efficient removal of drill dust and prevents clogging. Cuts nice， clean holes with very little or no chipping; operate drill motor 400-600 RPM