... granite, quartz, ironstone, chert, abrasive rock etc. Including impregnated diamond core bit, surface-set diamond bit, reaming shells, casing bit, casing shoe bit, corelifter, corelifter case, core ... selected grades of high quality synthetic diamond are distributed in the depth of impregnated bit's matrix series. ... to expose new diamonds to the bits' cutting face as wear occurs. Fast penetration rate ...