Abstract: Machining apparatus comprises a boom displaceable along spaced rails and a carriage displaceable along the boom perpendicularly to the displacement direction of the boom. A machining station is adjustably supported on the carriage by three adjustment means to adjust a machine head, such as a milling cutter, towards and away from a workpiece disposed between the rails beneath the machining station. Adjustment of the machine head results from inaccuracies in the level of the rails and/or the displacement of the carriage. Variations in the level of the rails and/or carriage are determined by a respective sensor associated with each adjustment means which monitors a reference defined by a planar laser beam. Alternatively one of the three adjustment means between the machining station and the carriage may be replaced by a pivot with the third adjustment means being arranged to adjust the machine head relative to the remainder of the machining station.

Abstract: Machining apparatus comprises a boom rotatable about a pivot support within a cylindrical workpiece with a machining station, such as a milling cutter, mounted on the remote end of the boom. Two angularly spaced wheel units are provided on respective sides of the boom to support the boom on the workpiece. Each wheel unit has an actuator to raise or lower that side of the boom relative to the support surface. Variations in the level of the support surface are determined by sensors monitoring a reference such as a rigid template or a planar laser beam. Each actuator has a respective sensor for independently adjusting each wheel unit and each sensor may be on a radius from the pivot to the associated wheel unit.In an alternative embodiment, the boom is linearly displaceable along spaced rails and the machining station is displaceable perpendicularly to the linear direction along the boom.