Patent ID: 8371775

Claim:
A shank attachment structure capable of detachably attaching a shank of a cutter to a tubular shank attachment hole with a single motion, the shank having at a base end portion thereof a concave portion for holding a part of an engaging member, and the shank attachment hole being formed such that: the engaging member projects radially inwardly from an inner peripheral surface of the shank attachment hole and is able to move radially outwardly therefrom; a longitudinal direction of the shank attachment hole extends in a body portion of an arbor in an axial direction of the arbor; and a tip end of the shank attachment hole opens on a tip end surface of the body portion, wherein: a coolant supplying hole is formed at a central portion of the body portion in a radial direction of the body portion and is adjacent to a base end side of the shank attachment hole such that a tip end of the coolant supplying hole communicates with the shank attachment hole; a valve body is disposed at a tip end portion of the coolant supplying hole so as to be movable toward a base end side, and a sealing member is disposed at a position of the coolant supplying hole which is closer to a tip end side than the valve body and contacts the valve body to form a fluid-tight state between the valve body and the sealing member; a first sleeve is disposed in the shank attachment hole such that: a base end of the shank contacts a tip end of the first sleeve to cause the first sleeve to move toward the base end side in the axial direction; a pressing portion contacts the valve body by this movement of the first sleeve to cause the valve body to be separated from the sealing member; in a state in which the shank is not in contact with the tip end of the first sleeve, an outer peripheral surface of the first sleeve having an outer diameter substantially equal to a diameter of the shank attachment hole causes the engaging member to move radially outwardly from an inner peripheral surface of the shank attachment hole; and a valve body operating member having at a base end thereof the pressing portion which presses the valve body to cause the valve body to be separated from the sealing member and having at a tip end thereof a contact surface which is contacted by the shank is disposed in the shank attachment hole.