... bits, sizes from 4" to 12-1/4" and diamond core bits. PDC bit----PDC inserts are set in a cast matrix head using ... round premium 13.4mm inserts. PDC bit are widely used in coalfields exploration and for open hole drilling. They possess high penetration ... as coal, oil shale, tarsands, and shallow oil and gas. PDC bit : sizes from 4" to 12-1/4",PDC core bit : BQ, NQ, NQ3, HQ ...