The present invention aims to provide a backdrilling method and a backdrilling apparatus that can ensure the backdrilling depth accuracy. Using a multilayer printed wiring board in which a reference depth detection region is allocated where a reference depth detection layer is formed in the same layer with an internal wiring layer electrically connected to a stub, the thickness and the depth of the reference depth detection layer are measured in the reference depth detection region using a drill bit. The drill bit is moved relative to the multilayer printed wiring board to a backdrilling portion. The drilling is performed using the drill bit to the depth which is calculated using the ratio of the depth of the reference depth detection layer to the thickness of the multilayer printed wiring board in the reference depth detection region.

A power tool includes a control for the motor of the power tool that senses an operating characteristic of the motor and controls the operation of the power tool based on the sensed characteristic. The sensed characteristic includes variations in reluctance of the motor. A controller may sense changes on load on the motor as a result of interaction between a working element such as a saw blade or drill bit and the work piece. The controlled operation may include variation in speed or torque or both, or may include stopping the motor. Emergency conditions may be sensed by changes in reluctance.

A machine tool control device which reliably divides and discharges chips, and which suppresses damage to a tool by reducing shock when the tool cuts into a workpiece. The machine tool control device causes the tool to rotate and executes a cutting process to move the tool and the workpiece while causing the same to oscillate relative to one another in a feed direction, and is provided with an oscillation command generating unit which generates an oscillation command on the basis of a predetermined oscillation condition. A position and speed control unit controls a motor by superimposing the oscillation command generated by the oscillation command generating unit onto a position command or a position deviation. The oscillation command generating unit changes an oscillation command phase progression method and/or an oscillation command amplitude on the basis of an oscillation phase calculated from on a predetermined oscillation condition, or based on time.