A method for performing a cutting operation on a workpiece is provided. The method comprises providing a workpiece being made of a metal characterized by a thermal conductivity of no greater than about 100 W100 .sup.W/.sub.(m.Math.K) (approximately 57.8 .sup.Btu/.sub.(hr ft ° F.)), providing a cutting device comprising an internal cooling cavity defined on one side thereof by a thin-walled structure, and performing a cutting operation on the workpiece using the cutting device. The cutting speed is no less than about 500 .sup.m/.sub.min. (approximately 1640 .sup.ft/.sub.min).

A blade in which coolant can be efficiently supplied to a machining place with a reduced pressure loss is provided. In a blade 100 in which a cutting insert 13 is attached to an insert attachment portion 12 provided at a longitudinal end part of a blade body 11 formed in a long plate shape, the blade body 11 includes a supply inlet 51 opened at one side surface, a lower discharge port 53 and an upper discharge port 54 that are opened at an end face nearby the insert attachment portion 12, a lower coolant supply path 55 connecting the supply inlet 51 to the lower discharge port 53, and an upper coolant supply path 56 connecting the supply inlet 51 to the upper discharge port 54, and the lower coolant supply path 55 and the upper coolant supply path 56 each have a curved shape in a side view.

A cutting insert comprising a cutting tip and a base insert on which the cutting tip is mounted, the cutting insert being provided with a passage PA which is formed along a boundary surface between the cutting tip and the base insert so as to extend from a boundary part, in an upper surface of the cutting insert, between the cutting tip and the base insert to another boundary part, in a lower surface of the cutting insert, between the cutting tip and the base insert.

A tool holder includes a receiving body, an interface at the rear for receiving the tool holder in a machine tool, a receiving section at the front for the tool, and a coolant bore arranged between the interface and the receiving section and by which coolant is conducted from the interface to the receiving section. The coolant bore has a first region with an adjoining second region. A coolant tube is arranged in the first region of the coolant bore. In the direction of the receiving section, between the coolant tube and the second region of the coolant bore, a cavity is formed in the receiving body or in the first region. A bridging element through which the coolant can flow and which seals the coolant flow in relation to the cavity is arranged in the cavity between the coolant tube and an interface-side end of the second region.

A body of a cutting tool has: an insert pocket in which a cutting insert is mounted; a screw hole into which an insert mounting screw for fastening the cutting insert to the insert pocket is screw-inserted; and a chip removal coolant flow path for allowing coolant C to be discharged through a discharge port that is open at a leading end of the body, wherein at least a part of the chip removal coolant flow path is at respective distances Da, Db and Dc from the insert pocket, from the screw hole, and from the periphery of the body, in a cross-section perpendicular to the axial direction of the body, wherein each of the distances Da, Db and Dc is equal to or greater than a predetermined size.

A cutting insert in an aspect of the present disclosure has a cutting part. The cutting part has a first surface, a second surface, a third surface located between the first surface and the second surface, and a flow path extending from the first surface toward the second surface. The flow path has an outflow port opening into the first surface, and a first flow path extending from the outflow port toward the second surface. In a first cross section that passes through a central axis of the first flow path and is orthogonal to the first surface, a width of the first flow path in a direction parallel to the first surface increases as going away from the first surface.