UTENSILE PER FORARE E ALESARE

A drilling and boring tool has a housing (3) which is provided at the front end of a holder shaft (1), a slide member (4) which is radially displaceable in the housing (3) with respect to the axis (A) of the holder shaft (1) by means of a screwthreaded spindle (5) and which bears against the inside of a cover plate (7) closing the housing (B) in a forward direction. The slide member (4) has a cylindrical spigot (9) which projects through an opening (8) in the cover plate (7). The shank portion (10a) of the tool receives the spigot (9) in a fitting bore (11), and bears with an annular surface (12) against the face (7b) of the plate (7). Two diametrically oppositely disposed, radially extending female screwthreads (13,14) each have a clamping screw (15,16) provided with a conical projection (15a) or a conical depression (16a) which engages a clamping pin (8) radially displaceable in a transverse bore (17) in the spigot (9). The clamping pin has a conical depression (19a) or a conical projection (19b), respectively co-operating with the conical projection (15a) or depressions (16a) of the clamping screw (15,16). The axis (A1) of the female screwthreads (13,14) is further from the annular surface (12) than the axis (A2) of the transverse bore (17) is from the front face (7b), so that when one of the clamping screws (15,16) is tightened, it acts on the clamping pin (18) to press the annular surface (12) and the front face (7b) towards each other.