CPC Subgroup
E21B 4/16 Plural down-hole drives, e.g. for combined percussion and rotary drilling (E21B4/10 takes precedence); Drives for multi-bit drilling units
Full Title
Drives for drilling, used in the borehole > Plural down-hole drives, e.g. for combined percussion and rotary drilling (E21B4/10 takes precedence); Drives for multi-bit drilling units