OFFSET TOOL

PURPOSE:To promote the miniaturization of a device, by rotatably providing a connecting means, which can be mounted to and removed from a main spindle, in a casing and a tool holder in a condition that it is eccentrically positioned from the axial center of the connecting means and enabling the casing to be turned about the axial center. CONSTITUTION:A connecting shaft 11b, which is rotatably provided in a casing 11a of an offset tool 11, is removably mounted to a main spindle 3. While providing a tool holder 11e in the casing 11a to be placed in an eccentric distance OFT1 from the main spindle center CT1, rotation of the connecting shaft 11b is transmitted to the holder 11e through gear 11d, 11f. While the casing 11, in which a rotatable turning gear 11i is mounted to the connecting shaft 11b, is able to turn about the connecting shaft 11b by a gear 21. Accordingly, if the gear 21a is rotated by a predetermined degree, the holder 11e is turned by the predetermined angle with the casing 11 around the axial center CT1.