In order to preserve the shape of your expensive shaped router bits it is very important that you break the sharp corners of the stone. You could use a dry diamond cup wheel, but this generates a fine dust that can be harmful. A better way is to use a CONFORM PRE-SHAPING ROUTER BIT [POS 0], specifically designed to quickly grind the corner of the stone in preparation for the shaping bit. Corner grinding quickly wears your shaping bits, this is why we provide the PRE-SHAPING routers with an EXTRA THICK layer of EXTRA COARSE DIAMOND. CONFORM Pre-Shaping routers bits are available to pre-shape for 20mm, 30mm Ogee or 40MM OGEE; or a special adjustable Fullbullnose breaker bit for any thickness up to 40mm.