The surface set natural diamond core bits are set with the premium natural diamond. crown type include step, discharge... China drilling Geological Equipment ltd., ... NQ HQ PQ T2 T6 etc. Diamond core bit, reaming shell & shoe bit (syn. and surface-set, PDC)4.Drill tool: hoisting ... ), overshot, outer tube & inner tube wrench, foot clamp etc. Surface Set natural Diamond Core Bits (step, discharge crown)