Abstract: A rock drilling tool includes a drill body on which a radially extendible reamer is mounted. The reamer, when extended, enlarges the hole diameter to enable a hole casing to be pulled down by the tool. The body includes a front pilot bit, a rear shank adapted to be connected to a drill string, and a guiding member disposed between the pilot bit and the rear shank for pulling the hole casing along with the tool. The pilot bit, the rear shank and the guiding member are non-removable from one another. The reamer, which is mounted between the guiding member and the pilot bit, is formed of two U-shaped pieces that are hinged together to enable the reamer to be installed and removed.

Abstract: A percussion drill bit includes a drill body having a fluid passage formed therein for conducting flushing fluid to a front drilling face of the drill bit. The fluid passage includes a main portion extending from a rear end of the bit and terminating short of the drilling face, and a plurality of branch lines extending from a front end of the main portion to the drilling face. Front and rear axially spaced seats are disposed in the main portion of the fluid passage. A check valve in the form of a ball is freely movable within the main portion of the fluid passage between contact with the front and rear seats. When the drill bit is oriented upwardly and no flushing fluid is supplied, the ball gravitates rearwardly into sealing contact with the rear seat so that no fluid can flow rearwardly past the rear seat. When flushing fluid is conducted, the flushing fluid pushes the ball forwardly, into non-sealing contact with the front seat and travels past the ball into the branch lines.