The tool holder has a pocket for an indexable insert (20) which has a positive rake angle. The cutting edges of the insert project over the rake faces which each have central plateau sections which lie parallel to the equivalent section of the opposite side of the insert. Certain dimensions of the support surface of the pocket of the tool holder are greater or the same as matching radial distances on the insert. The pocket support surface and the insert when assembled in the clamped condition have a common contact area.
