... kinds of diamond core bits in different size, which are used in shale, sandstone, limestone, marble, dolomite, schist, granite, ... rock etc. Including impregnated diamond core bit, surface-set diamond bit, reaming shells, casing bit, casing shoe bit, corelifter, corelifter case, core barrel ... bits are manufactured to give optimum penetration rates and bit life, which is required to keep the cost of ...