A virtual plane obtained by a locus when a tangent line, which passes through a tool distal end edge, of a virtual circle formed when a tool distal end edge of a cutting edge is rotated in a tool circumferential direction is moved parallel to a tool axial line is a reference plane, an angle (ARt) at which a cross line of the reference plane and the cutting edge virtual plane, is inclined with respect to the tool axial line projected onto the reference plane, is in a range of 30 degrees to 60 degrees, an angle (RR) at which a cutting edge tangent line which passes through the tool distal end edge and extends outward in a tool radial direction, is inclined with respect to a predetermined tool radial direction, which passes through the tool distal end edge, is in a range of 30 degrees to 75 degrees.

A virtual plane obtained by a locus when a tangent line, which passes through a tool distal end edge, of a virtual circle formed when a tool distal end edge of a cutting edge is rotated in a tool circumferential direction is moved parallel to a tool axial line is a reference plane, an angle (ARt) at which a cross line of the reference plane and the cutting edge virtual plane, is inclined with respect to the tool axial line projected onto the reference plane, is in a range of 30 degrees to 60 degrees, an angle (RR) at which a cutting edge tangent line which passes through the tool distal end edge and extends outward in a tool radial direction, is inclined with respect to a predetermined tool radial direction, which passes through the tool distal end edge, is in a range of 30 degrees to 75 degrees.

A cutting insert comprising a cutting edge formed by an intersection ridge between a rake face and a side face, the cutting edge including a major cutting edge, a flat cutting edge, and a chamfer edge disposed between the major cutting edge and the flat cutting edge, wherein in a direct view of a side face near the flat cutting edge, a ratio of installation area length L2 of the chamfer edge to installation area length L3 of the major cutting edge is L2:L3=2:8 to 5:5, and inclination angle .sub.1 of the chamfer edge with respect to the flat cutting edge and inclination angle .sub.2 of the major cutting edge with respect to the flat cutting edge are set to have a relationship of .sub.1<.sub.2.

A cutting insert comprising a cutting edge formed by an intersection ridge between a rake face and a side face, the cutting edge including a major cutting edge, a flat cutting edge, and a chamfer edge disposed between the major cutting edge and the flat cutting edge, wherein in a direct view of a side face near the flat cutting edge, a ratio of installation area length L2 of the chamfer edge to installation area length L3 of the major cutting edge is L2:L3=2:8 to 5:5, and inclination angle .sub.1 of the chamfer edge with respect to the flat cutting edge and inclination angle .sub.2 of the major cutting edge with respect to the flat cutting edge are set to have a relationship of .sub.1<.sub.2.

A method for milling a planar surface, during which a milling cutter, an axis of rotation of which is perpendicular to a surface to be machined, is moved in a direction parallel to the plane of the surface, to machine the surface in a single machining operation, over a predetermined layer of material, using a single milling head, and the milling cutter, in a same axial position relative to the surface to be machined, simultaneously carries out rough working, at least one intermediate finishing operation, and a finishing operation over a same layer of material.

A rotary cutting tool includes a tool holder and a tool body releasably attached thereto. The tool body has a cutting portion that includes a peripheral insert pocket, for retaining a cutting insert. The tool holder includes an adjustment arrangement that includes a biasing member, movably attached to the tool holder, having a biasing portion. The cutting portion is adjustable between a non-flexed position and a flexed position. In the flexed position, the cutting portion is elastically deformed in a forward direction due to biasing engagement with the biasing portion, thereby adjusting the axial position of the insert pocket and thus the cutting insert.

A rotary cutting tool includes a tool holder and a tool body releasably attached thereto. The tool body has a cutting portion that includes a peripheral insert pocket, for retaining a cutting insert. The tool holder includes an adjustment arrangement that includes a biasing member, movably attached to the tool holder, having a biasing portion. The cutting portion is adjustable between a non-flexed position and a flexed position. In the flexed position, the cutting portion is elastically deformed in a forward direction due to biasing engagement with the biasing portion, thereby adjusting the axial position of the insert pocket and thus the cutting insert.

Cutting insert with a cuboid body has a substantially square top face and bottom face, said top face and bottom face connected by four peripheral adjoining side surfaces. At least two cutting edges are formed at the transition of the top face to at least two side surfaces, that cutting edges defining a plane of the top face. To provide a cutting insert and a corresponding tool suited to produce valve seat surfaces with high precision but still having a rather simple construction and being precisely mountable with ease and less efforts of adjustment, the plane defined by the top face cutting edges of the cutting insert has maximum dimensions of 7 mm7 mm, where the bottom face has a supporting surface formed exactly parallel to the plane defined by the top face cutting edges by means of grinding within a tolerance of less than 5 angular minutes.

Cutting insert with a cuboid body has a substantially square top face and bottom face, said top face and bottom face connected by four peripheral adjoining side surfaces. At least two cutting edges are formed at the transition of the top face to at least two side surfaces, that cutting edges defining a plane of the top face. To provide a cutting insert and a corresponding tool suited to produce valve seat surfaces with high precision but still having a rather simple construction and being precisely mountable with ease and less efforts of adjustment, the plane defined by the top face cutting edges of the cutting insert has maximum dimensions of 7 mm7 mm, where the bottom face has a supporting surface formed exactly parallel to the plane defined by the top face cutting edges by means of grinding within a tolerance of less than 5 angular minutes.

An indexable milling cutting insert includes an opposed outside and inside, a periphery, and a plurality of homologous and alternately individually usable cutting edges, which are equidistantly spaced apart from a centre axis, which extends between the outside and inside. The cutting insert includes a plurality of countersunk chip channels, which are delimited by bottoms and tangentially spaced-apart ridges, which individually include a cutting edge formed between a chip surface included in a first chip channel, and a clearance surface, which borders on a second chip channel.