3/16" Groove Bit For Porcelain, Granite, Marble & Ceramic 25 Pack. Drilling hard material like hard tile, porcelain, granite, marble and ceramic is just that, hard! These carbide tip bits are especially designed for these hard applications. The carbide tip features grooves to keep the bit from "walking" on the hard surface and aids in getting the dust out of the way. You will want to use a higher speed and make sure you dip the bit regularly in water to keep them cool for best results. Keep in mind these are designed to bused in rotary mode only, no hammer drilling! Check the video below for best results.