A turning tool includes a tool body and a turning insert, and an insert seat in which the turning insert is mounted. The insert seat includes a bottom surface and a side surface, the side surface having a first surface and a second surface. The first surface includes a contact surface, wherein the contact surface is in contact with a portion of the side surface of the turning insert. The tool body includes a coolant channel, which extends between a coolant channel inlet and a coolant channel outlet opening into a void between the side surface of the turning insert and the first surface of the side surface of the insert seat.

A cutting insert according to an aspect includes a base portion and a cutting portion. The cutting portion includes a front end surface, an top surface, a first lateral surface, a second lateral surface, a front cutting edge, and a lateral cutting edge. The front cutting edge includes a first cutting edge and a second cutting edge, and a radius of curvature of the first cutting edge is greater than a radius of curvature of the second cutting edge.

A cutting insert may include a base and a cutting part. The cutting part may include an upper surface, a first cutting edge and a second cutting edge. The first cutting edge may be located on a first ridgeline. The second cutting edge may be located on a second ridgeline. The upper surface may include a first inclined surface, protrusions and a first upheaved part. The first inclined surface may be located along the first ridgeline. The protrusions may be located side by side in a direction along the first ridgeline on the first inclined surface. The first upheaved part may be located at a side further away from the first ridgeline than the pair of protrusions. The second cutting edge may be inclined downward. An upper end of the first upheaved part may be located above the second cutting edge.

There is provided a cutting insert having a low possibility that chips roughen a machined surface of a workpiece in back turning. The cutting insert includes a rake surface, a peripheral side surface, a front cutting edge which is provided on a ridge of the rake surface and the peripheral side surface, and a main cutting edge which is provided on the ridge so as to be continuous with the front cutting edge and has an extension direction which forms an obtuse angle with an extension direction of the front cutting edge, the main cutting edge is curved into a U shape over an entire length of an effective edge range which functions as a cutting blade, and the deepest point of the U shape is positioned in a range closer to a side of a corner than a position which divides a straight line connecting both ends of the main cutting edge at a ratio of 2:1 from the side of the corner positioned adjacent to the front cutting edge.

A single-crystal diamond cutting tool is provided with a flank and a rake face, a cutting edge being provided at a boundary between the flank and the rake face, an inclined surface being provided at a location distant from the cutting edge, the inclined surface being contiguous to the rake face and inclined at 0.05 degrees or more and 80 degrees or less with respect to the rake face, the rake face having a roughness Ra of 1 .Math.m or less, the cutting edge being provided with a chamfered surface or round honing having a width of 1 .Math.m or less, the cutting edge having projections and depressions having a width of 100 nm or less and smaller than that of the chamfered surface or round honing.

A turning insert includes a top surface, a bottom surface, and side surfaces connecting the top and bottom surfaces. A reference plane is located parallel to and between the top surface and the bottom surface. A center axis intersects and extends perpendicular to the reference plane. Three nose portions are formed symmetrically around the center axis. Each nose portion has a first cutting edge, a second cutting edge and a convex nose cutting edge connecting the first and second cutting edges. As seen in in a top view, the first and second cutting edges on the same nose portion form a nose angle of 25-50°. The first cutting edge includes a first sub-portion and a second sub-portion. A distance from the nose cutting edge to the first sub-portion is shorter than a distance from the nose cutting edge to the second sub-portion.

There is provided a cutting tool in which chip control is improved. A cutting edge member includes a first wall surface which includes a concave surface which is formed to be depressed in a direction away from an intersection point of an imaginary plane and a corner portion and toward the center of a cutting insert in an end view when viewed from a direction facing an end surface, a second wall surface which includes a convex surface which is provided to be connected to the first wall surface at a position spaced apart from the imaginary plane and is protruded in a direction away from the center of the cutting insert in the end view, a third wall surface which includes a convex surface which is provided to be connected to the first wall surface at a position spaced apart from the imaginary plane on an opposite side to the second wall surface across the imaginary plane and is protruded in a direction away from the center of the cutting insert in the end view, and a fourth wall surface which is provided in an area between the first wall surface and the intersection point in the end view, includes a convex surface which is protruded in a direction away from the center of the cutting insert in the end view, and has a height smaller than heights of the second wall surface and the third wall surface in a side view when viewed from a direction facing a side surface.

It is intended to allow a wide range including a low region (fine finishing) to a middle region (medium cutting) to be covered with a single insert. A cutting insert includes an upper surface, a lower surface, a peripheral side surface, a cutting edge including a main cutting edge and a corner cutting edge, a corner portion, a projecting portion formed to extend from the corner portion toward a central axis and including a first projection and a second projection, a rake portion, and an inclined portion provided at the cutting edge. The inclined portion has a first inclined portion beginning at an intermediate point in the corner cutting edge, while the rake portion has a shape in which an angular degree of a rake angle gradually increases with distance from the corner portion.

A cutting insert may include a first surface, a second surface and a third surface. The first surface may include a corner having a convex curvilinear shape and an inclined surface. The inclined surface may include a first inclined surface, a second inclined surface and a third inclined surface. The first inclined surface may be inclined at a first angle. The second inclined surface may be inclined at a second angle. The third inclined surface may be inclined at a third angle. The first inclined surface may have a concave curvilinear shape in a cross section orthogonal to a bisector of the corner. The second inclined surface may be a flat surface. The second angle may be smaller than either of the first angle and the third angle in a cross section which includes the bisector and is orthogonal to the reference plane.

A turning insert includes a top surface, an opposite bottom surface, and a reference plane located parallel to and between the top and the bottom surfaces. A nose portion includes a convex nose cutting edge, and a first and a second cutting edge. The nose cutting edge connects the first and second cutting edges. The first and second cutting edges form a nose angle of 71-85° relative to each other. The nose portion has a third convex cutting edge adjacent to the first cutting edge and a fourth cutting edge adjacent to the third convex cutting edge. The fourth cutting edge forms an angle of 10-30° relative to a bisector. The distance from at least a portion of the fourth cutting edge to the reference plane increases at an increasing distance from the nose cutting edge. A second protrusion is arranged between the nose cutting edge and the first protrusion.