Device for monitoring the position of a tool or machine element

Device for monitoring the position of a tool (4) or machine element (30) on or in a work spindle (1) or a tool chuck (27), in particular in a machining apparatus, wherein the work spindle (1) or tool chuck (27) has at least one channel (5, 6, 7′ 35, 36) that defines a waveguide for propagating electromagnetic waves that leads from an outer surface of work spindle (1) or tool chuck (27) to tool (4) or machine element (30), and in that at least one radar system (11;

• 37) is provided and arranged outside work spindle (1) or tool chuck (27) in such a manner that it is capable of irradiating a radar signal from the outer surface into channel (5, 6, 7;
• 35, 36) and of receiving a radar signal reflected back out of channel (5, 6, 7;
• 35, 36), and in that radar system (11;
• 37) is connected to a signal-processing device (18, 19, 20;
• 26) that determines a measure of the position of tool (4) or machine element (30) in relation to work spindle (1) or tool chuck (27) based on at least one radar signal irradiated into channel (5, 6, 7;
• 35, 36) and reflected out of channel (5, 6, 7;
• 35, 36).