A hub flange has a fixed flange configured to receive a tool body. A flange socket is formed on the fixed flange for connection to a spindle shaft. A counterflange is detachably connected to the fixed flange. The fixed flange and the counterflange are connected to each other via a conical connection, wherein the conical connection is arranged coaxially to the tool axis and is formed by an inner cone and an outer cone received therein.

A grinding arm for grinding workpieces with an inner profile with a grinding wheel. The grinding arm has a tube-shaped base body with a longitudinal axis, in which the grinding wheel is supported at one axial end region. A first drive for the grinding wheel is arranged in its other axial end region. A first transmission system transmits the rotation from the first drive to the grinding wheel. In order to adjust arbitrary angles of inclination of the grinding wheel in the grinding arm, the grinding wheel is arranged on a grinding spindle driven by the first transmission system and rotating around an axis of rotation. The grinding spindle is supported in a carrier body arranged in the base body rotatable around an axis perpendicular to the longitudinal axis as well as perpendicular to the axis of rotation, wherein the axis of rotation and the axis intersect.

A grinding arm for grinding workpieces with an inner profile with a grinding wheel. The grinding arm has a tube-shaped base body with a longitudinal axis, in which the grinding wheel is supported at one axial end region. A first drive for the grinding wheel is arranged in its other axial end region. A first transmission system transmits the rotation from the first drive to the grinding wheel. In order to adjust arbitrary angles of inclination of the grinding wheel in the grinding arm, the grinding wheel is arranged on a grinding spindle driven by the first transmission system and rotating around an axis of rotation. The grinding spindle is supported in a carrier body arranged in the base body rotatable around an axis perpendicular to the longitudinal axis as well as perpendicular to the axis of rotation, wherein the axis of rotation and the axis intersect.

A method for clamping a tool on a tool spindle in a hard finishing machine that includes: the tool spindle connected to a drive motor, with a cylindrical receiving seat and a thread, and the tool. The receiving seat is limited at one axial position of the tool spindle by a abutment flange for axial abutment of the tool. A clamping nut can be screwed onto the thread and is designed for axial abutment on the tool. The clamping nut is temporarily held in a rotationally fixed manner when the tool spindle is rotated by the drive motor. The method includes: placing the tool on the receiving seat and screwing the clamping nut onto the thread; blocking the clamping nut against rotation during the rotation of the tool spindle with the drive motor; and actuating the drive motor to tighten the clamping nut so it presses axially against the tool.