Abstract: The apparatus is intended for securing a tool (3) in a holder (1), of which one (1) having a hole (2) and the other (3) having a stem (4) fitted in the hole (2), the stem surface being provided with a groove (7) having side surfaces (8, 9). The apparatus comprises a pin (10). The hole (2) and the stem (4) have bearing surfaces (12, 13). The minimum distance (1) from the bearing surface (13) of the stem (4) to the side surface (8) of the groove (7) farthest therefrom is less than the distance (L) from the bearing surface (12) of the hole (2) to the surface of the pin (10) farthest from said bearing surface (12) of the hole (2).

Abstract: A reamer is provided with teeth (3) having a cutting portion (4) and a smoothing portion (5), wherein at least part of the rear surface of the latter portion is fashioned as a strip. Each tooth (3) has its front angle smoothly decreasing in the direction away from the head portion (6) of the reamer.

Abstract: A cutting-off tool comprises a holder (1) and a disk cutter member (2) with recesses (4) being interconnected by means of the bushings (5) having projections (6) which are received in the respective recesses (4) of the cutting-off tool (2) and wedge-and-screw mechanisms which interact with the cutting-off tool (2). Each bushing (5) has a longitudinal groove (13) leading out on its end face having the projection (6).

Abstract: A drill comprises a holder (1) and a cutting member in the form of a pair of discs (2,3). Each disc (2,3) has at least five facets (11,12) arranged along its periphery and symmetrically with respect to its center line (13, 14), the discs (2, 3) being mounted in such a manner that angles (.phi.) of inclination of their facets (11, 12) with respect to an axis (4) of the holder (1) are equal to one another.