Abstract: A moveable and demountable workpiece processing bench includes a hollow mounting beam for mounting equipment, a workpiece processing tool releasably mounted on the mounting beam, a positioning arm which is mounted movably in a longitudinal direction inside the hollow mounting beam and which includes a workpiece stopper at an end distal from the workpiece processing tool, and a drive unit, mounted on the mounting beam. The drive unit includes displacement means configured to move the positioning arm to a desired position. The displacement means includes a gear drive, which engages in a rack of teeth on the positioning arm to move the positioning arm to a desired position; and a length control unit for controlling the displacement means.