BLADE CHANGE UNIT

A blade changer unit has a blade clamping device for holding a cutting blade， a movement unit for moving the blade clamping device and a control unit for controlling a movement unit. The blade clamping device has a plurality of electrically conductive grippers for holding the cutting blade. The controller detects a line between the grippers and a hub. The control unit has a computer for calculating the position of a central axis of the attachment from coordinates at which the line between the holder and the hub is detected when the movement unit is controlled to bring the grippers into contact with the attachment at at least three points ， and an attachment / detachment control for attaching and detaching the cutting blade， while the central axis of the blade clamping device is aligned with the central axis of the attachment calculated by the computer.