A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

Provided is a coated cutting tool having improved wear resistance and fracture resistance and a long tool life. The coated cutting tool includes a substrate, and a coating layer formed on a surface of the substrate. The coating layer has a laminated structure in which a first layer and a second layer are alternately laminated for one or more layers. The first layer is a compound layer having a composition represented by Ti(C.sub.xN.sub.1-x). The second layer is a compound layer having a composition represented by (Ti.sub.yAl.sub.1-y)N. The laminated structure includes first to third laminated structures in this order from a substrate side to a surface side of the coating layer. An average thickness per layer of each of the first layer and the second layer in the first to third laminated structures is in a specific range. An average thickness of the first to third laminated structures is in a specific range.

A method for producing a coated cutting tool for metal machining having a substrate and coating is provided. The coating includes at least one layer of (Ti,Al)N having a cubic crystal phase. The method includes the deposition of a layer of Ti.sub.1-xAl.sub.xN, 0.70≤x≤0.98, the Ti.sub.1-xAl.sub.xN having cubic crystal phase. The layer of Ti.sub.1-xAl.sub.xN is deposited by cathodic arc evaporation at a vacuum chamber pressure of from 7 to 15 Pa of N.sub.2 gas, using a DC bias voltage of from −200 to −400 V and using an arc discharge current of from 75 to 250 A. A coated cutting tool for metal machining having a coating including a (Ti,Al)N multi-layer of alternating sub-layers of at least Ti.sub.1-yAl.sub.yN and Ti.sub.1-zAl.sub.zN, 0.35≤y≤0.65 and 0.80≤z≤0.98, with only cubic phase present is also provided.

A coated cutting tool includes a substrate and a coating, wherein the coating has a (Ti,Al)N multilayer of alternating cubic Ti.sub.1-xAl.sub.xN sub-layers, 0.60≤x≤0.75, and cubic+hexagonal Ti.sub.1-yAl.sub.yN sub-layers, 0.60≤y≤0.75. The average cubic Ti.sub.1-xAl.sub.xN sub-layer thickness is from 75 to 450 nm and the average cubic+hexagonal Ti.sub.1-yAl.sub.yN sub-layer thickness is from 50 to 300 nm. The number of each of the cubic Ti.sub.1-xAl.sub.xN sub-layers and cubic+hexagonal Ti.sub.1-yAl.sub.yN sub-layers is from 2 to 50.

A cutting tool comprises a substrate and an AlTiN layer, the AlTiN layer including cubic Al.sub.xTi.sub.(1-x)N crystal grains, an atomic ratio x of Al in the Al.sub.xTi.sub.(1-x)N being 0.7 or more and 0.95 or less, the AlTiN layer including a first major surface on a side of a surface of the cutting tool and a second major surface on a side of the substrate, the AlTiN layer including a first region having a distance of 0 nm or more and 100 nm or less from the first major surface, and a second region having a distance of more than 100 nm and 150 nm or less from the first major surface, the first region having a maximum oxygen content ratio of 5 atomic % or more and 30 atomic % or less, the second region having a maximum oxygen content ratio of less than 5 atomic %.

A cutting insert of a substantially horizontal cylindrical segment shape may include top and bottom surfaces having a circular segment shape. The cutting insert may include a convex side and a flat side. The cutting insert may include a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert may include a hole extending from the convex side towards the flat side. The hole may be positioned at a center of a surface of the flat side.