Abstract: The mounting body (1) of the boring tool, which is of a hub-like configuration, is provided, at locations which are diametrally oppositely disposed with respect to the axis of rotation (D) of the mounting body, with a respective mounting bore (3) with its axis (A) extending radially with respect to the axis of rotation (D), the mounting bore being surrounded by a respective abutment surface (4) extending perpendicularly with respect to the axis (A) of the mounting bore (3). A tool head (5) is provided with a fitting spigot (6) which fits into the mounting bore (3) and which is concentrically surrounded by an annular surface (7) extending perpendicularly with respect to the axis (A) of the fitting spigot. A respective intermediate portion can optionally be fitted between the mounting body (1) and the respective tool head (5), the connecting parts of the intermediate portion corresponding to those of the mounting body (1) and the tool head (5).

Abstract: A tool holder with radial adjustment means. The tool holder has a connecting portion having a connecting shank, an intermediate portion and a head portion, and a tool receiving means for a tool, in particular a rotary tool. All three portions (2, 3, 4) are of substantially disc-like configuration and bear against each other with their faces (2a, 3a, 3b, 4a) which extend radially with respect to the axis (A) of the connecting shank. Provided at the periphery of the connecting portion (2) are two diametrally oppositely disposed recesses (8) into which two claws (9) arranged on the intermediate portion engage with radial play. Provided at the periphery of the intermediate portion (3) are two diametrally oppositely disposed recesses (14) which are displaced through 90.degree. relative to the claws (9) and into which two claws (15) disposed on the head portion (4) engage with radial play.