The porcelain and tile drill bit is a new generation of carbide drill bits it has a positive and a negative cut which makes the drill extremely sharp and allows aggressive drilling suitable for all kinds of porcelain tiles and fine stoneware at low speed approx 400 600 revolutions per minute also very well suited for cordless power drills there is no centering device and no cooling necessary when using these bits for drilling holes larger than 5 mm it should be pre drilled with a 4 mm