Hammer drilling devices

A rotational drilling device comprising in combination two releasably connected parts, one of said two parts being a drill with a substantially cylindrical shaft and the other of said two parts being a tool receiving means with a substantially cylindrical bore in which said shaft is received for limited axial movement, said tool receiving means being adapted for connection to rotatable and percussive drive means and having means for imparting rotative and percussive movement to said drill, one of said two parts comprising in relation to said shaft at least one radially extending element which is fixably secured and the other of said two parts comprising in relation to said shaft at least one substantially axially extending elongated recess, said recess having first and second closed axial ends opposite to each other, said recess having a radial depth which corresponds to the radial extension of said element, said recess having a transition surface starting at the radially deepest area of the recess and extending substantially concentrically in relation to the axis of said part provided with said recess, said transition surface starting at a position spaced from said first and second ends of the recess, said transition surface intersecting the longitudinal edge of the recess which is kept free from the transfer of the rotational force by said element, and a guiding surface open at one end and closed in axial direction at its opposite end and connected by said transition surface with said recess, said guiding surface having the same radial depth as said recess and being off-set in circumferential direction in relation to said recess.