Bolt-nut tightening device having means for preventing abnormal

Compressed-air screwdriver with shutoff bypass means

Concrete drop hammer attachment device

Construction of underground dams and equipment therefor

Control system for a rock drill

Control system for an internal combustion engine using either ga

Control system for percussion drill

Controls for hydraulic percussion drill

Damper pressure control apparatus for hydraulic rock drill

Device and method for installing ducts in holes produced by soil

Device for introducing additional air into intake passage leadin

Device for soil sampling under water

Device for the production of earth holes

Drill feed control utilizing a variable overcenter valve

Drill mounting device for backhoe attachments

Drill rig shut-off system

Drilled hole end adjusting arrangement

Dual motor torque delivering tool

Dual speed transmission for automatic assembly machine

Electric drill with speed and torque control