Abstract: A rock drill feed shell is slidably mounted on a support bracket and is connected to a feed screw which is threaded through a feed nut mounted on an elongated supporting tube disposed telescopically within the feed shell. The supporting tube is displaceable with respect to the support bracket by a feed extension cylinder mounted on the support bracket. A rock drill is slidably mounted on the feed shell and engages a second feed screw supported by the feed shell. A feed motor is drivably connected to both screws.

Abstract: A replaceable stabilizer comprises a steel sleeve with fixed blades adapted to be installed over the reduced lower box end of tubular rotary drill steel member prior to insertion of the taper threaded pin of a drill bit into the taper threaded drill steel box. The drill steel member may be a special sub or a regular length of drill steel with modified lower end. An internal straight thread at the upper end of the sleeve screws onto an external straight thread on the drill steel box. An annular rubber gasket secured to the upper end of the sleeve is clamped between the upper end of the sleeve and a shoulder on the steel between the main body and the reduced box end thereof. An inturned flange at the lower end of the sleeve is clamped between a shoulder provided by the mouth of the drill steel box and a shoulder on the drill bit around its taper threaded pin. Make up of the pin and box forms a rotary shouldered connection.

Abstract: A power tool having a cylindrical housing accomodating a hammer and a two-step defining piston head, with central, rear and supplementary chambers in the housing, said head and supplementary chambers being constantly intercommunicated through a passage provided in the housing. The design of the power tool is aimed at minimizing vibrations of the housing and reduction of the forces applied to the handle during normal operation of the power tool.