The precision spindle with SK40 - TC40 - DIN69871 shank connection is used to check the geometry of the machine tool spindle to ensure perfect geometric alignment with the various axes of the machine.
Generally, this check is carried out during maintenance or after a collision between the axis of the tool spindle and the axes of all the workpieces or slides on milling machines or machining centres. On a lathe, the bar is used to align the axes of the turret or tool holder spindles with the axis of rotation of the main spindle of the lathe.