... steel Certificated by API&ISO9001:2008 8 1/2" New PDC Bits for Well Drilling Description about sell rock bits,tricone bits ... different PDC (polycrystalline diamond compact) grades and shapes applied for rock formations as follows:1. Andesite, marble, metamorphic schist ... used in the field of mine, transportation, tunnel and hydroelectric for shelving reticular support.Model114,117,127,437,517,617,637 ...