Abstract: In order to implement simultaneous casing while drilling of larger diameter pile holes and water wells in complex strata, a new type of bit for simultaneous casing while reverse circulation drilling with DTH air hammer was developed. Its makeup, working principle and features of design are presented. Compared with conventional design, the new type reverse circulation bit for casing while drilling has several advantages. Novel passage design can improve the effectiveness of cuttings removal, result in cleaner hole, reduce fragmentation repeat, and speedup penetration. More peripheral carbon-tungsten teeth would improve the abrasion resistance and service life of the bit.

Key words: simultaneous casing while drilling, reverse circulation, passage for cuttings removal, pilot bit