... bits, sizes from 4" to 12-1/4" and diamond core bits. PDC bit----PDC inserts are set in a cast ... open hole drilling. They possess high penetration than conventional diamond core bit from soft to medium-hard formations, particularly in soft ... 12-1/4",PDC core bit : BQ, NQ, NQ3, HQ, HQ3, PQ, PQ3, T2 76, T2 86, T6101, T6 116, T2 131 and so on ...