Abstract: A horizontal rotary table is provided and a mounting arm is supported above the table and generally parallels the latter. The arm extends along a path paralleling an axis of rotation of the table and an upright shaft is journalled from the mounting arm for rotation about an upright axis coinciding with the axis of rotation of the table. Drive structure drivingly connects the table and the upright shaft for rotation of the latter at twice the speed of rotation of the table and a support is mounted on the support arm for guided movement therealong. A scribe tool is carried by the support for engagement with and scribing a workpiece disposed on the table for rotation with the latter and motion converting and drive structure is operatively connected between the upright shaft and the support for effecting oscillation of the support along the arm responsive to and an in timed relation with rotation of the shaft.