Recommended operating speed is between 700 and 900 Rpm. Renewing tip geometry, when the products life is exhausted in Porcelain, the PTB bit can be used in softer materials. The PTB 1/4" carbide bit is also used to drill a pilot hole necessary for use with the PTB water feed adapter for Diamond Crowns. Armeg PTB carbide drill bits can also be used in marble, granite, travertine, natural slate, quarry tiles, ceramic tiles, natural stone, limestone, rosemary roof tiles, etc.