... 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 ... drilling. They possess high penetration than conventional diamond core bit from soft to medium-hard formations, particularly in soft ... , tarsands, and shallow oil and gas. PDC bit : sizes from 4" to 12-1/4",PDC core ...