... 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 ... , tarsands, and shallow oil and gas. PDC bit : sizes from 4" to 12-1/4",PDC core bit : BQ, NQ, NQ3, HQ ... , T2 86, T6101, T6 116, T2 131 and so on. PDC Bit