Rotary cutting tool and tool assembly

A rotary cutting tool including a tool body comprising a central longitudinal axis (L) which forms an axis of rotation (L) of the cutting tool, wherein, at one axial end, the tool body comprises a cylindrical shank having at least one locking groove via which the cutting tool can be axially locked in a tool holder,

• wherein the locking groove has an axial groove, which extends from an axial end on a receiving side in axial direction (A) to an axial stop, and a circumferential groove, which is laterally adjacent to the axial groove and extends away from the axial stop and the axial groove in circumferential direction (U) toward a rotation stop, wherein
• the circumferential groove comprises a first end face and a second end face opposite to said first end face, wherein both the first and the second end face extend in a plane that is perpendicular to the axis of rotation (L), and
• wherein, in a sectional plane that is perpendicular to the axis of rotation (L), the axial groove has a lenticular cross-section with a radially outer section which is formed by an envelope on an outer circumference of the shank and a radially inner section which is formed by a circular arc.