A sintered body of the present invention is a sintered body including a first material and cubic boron nitride. The first material is partially-stabilized ZrO.sub.2 including 5 to 90 volume % of Al.sub.2O.sub.3 dispersed in crystal grain boundaries or crystal grains of partially-stabilized ZrO.sub.2.

In a diamond polycrystal, a value of a ratio (d′/d) of d′ to d is less than or equal to 0.98 in a Vickers hardness test performed under a condition defined in JIS Z 2244:2009, where the d represents a length of a diagonal line of a first Vickers indentation formed in a surface of the diamond polycrystal when a Vickers indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the d′ represents a length of a diagonal line of a second Vickers indentation remaining in the surface of the diamond polycrystal after releasing the test load.

In a diamond polycrystal, a value of a ratio (d′/d) of d′ to d is less than or equal to 0.98 in a Vickers hardness test performed under a condition defined in JIS Z 2244:2009, where the d represents a length of a diagonal line of a first Vickers indentation formed in a surface of the diamond polycrystal when a Vickers indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the d′ represents a length of a diagonal line of a second Vickers indentation remaining in the surface of the diamond polycrystal after releasing the test load.

A cutting tool comprises a substrate and a coating that coats the substrate, the coating including an α-alumina layer provided on the substrate, the α-alumina layer including crystal grains of α-alumina, the α-alumina layer including a lower portion and an upper portion, the upper portion being occupied in area at a ratio of 50% or more by crystal grains of α-alumina having a (006) plane with a normal thereto having a direction within ±15° with respect to a direction of the normal to the second interface, the lower portion being occupied in area at a ratio of 50% or more by crystal grains of α-alumina having a (110) plane with a normal thereto having a direction within ±15° with respect to the direction of the normal to the second interface, the α-alumina layer having a thickness of 3 μm or more and 20 μm or less.

A cutting tool comprises a substrate and a coating that coats the substrate, the coating including an α-alumina layer provided on the substrate, the α-alumina layer including crystal grains of α-alumina, the α-alumina layer including a lower portion and an upper portion, the upper portion being occupied in area at a ratio of 50% or more by crystal grains of α-alumina having a (006) plane with a normal thereto having a direction within ±15° with respect to a direction of the normal to the second interface, the lower portion being occupied in area at a ratio of 50% or more by crystal grains of α-alumina having a (110) plane with a normal thereto having a direction within ±15° with respect to the direction of the normal to the second interface, the α-alumina layer having a thickness of 3 μm or more and 20 μm or less.

A multi-part modular tool rotatable about a longitudinal tool axis (A), comprising: a machining head; a first holding element comprising a body elongated along the longitudinal axis (A) of the tool, in which a passage extends along the longitudinal axis (A) of the tool; a second holding element which can extend in the passage of the first holding element; wherein the machining head can be connected to the second holding element in such a way that the machining head is fixed firmly to the first holding element at least in the axial direction (A) and/or in the radial direction (R), and wherein the passage of the first holding element and the second holding element are adapted to one another such that during a connection process in which the machining head is connected to the second holding element, the second holding element is movable relative to the first holding element.

A coated cutting tool includes a substrate and a coating layer formed onto the surface of the substrate. The coating layer contains an outermost layer. The outermost layer contains NbN. The NbN contains cubic NbN and hexagonal NbN. When a peak intensity at a (200) plane of cubic NbN is made I.sub.c, a peak intensity at a (101) plane of the hexagonal NbN is made I.sub.h1, and a sum of peak intensities at a (103) plane and a (110) plane of the hexagonal NbN is made I.sub.h2 in X-ray diffraction analysis, a ratio [I.sub.h1/(I.sub.h1+I.sub.c)] of I.sub.h1 based on a sum of I.sub.c and I.sub.h1 is 0.5 or more and less than 1.0, and a ratio [I.sub.h1/(I.sub.h1+I.sub.h2)] of I.sub.h1 based on a sum of I.sub.h1 and I.sub.h2 is 0.5 or more and 1.0 or less.

A sialon sintered body and a cutting insert each having thermal shock resistance and VB wear resistance. The sialon sintered body and the cutting insert contain β-sialon and 21R-sialon and exhibit an X-ray diffraction peak intensity ratio R[(I.sub.21R/I.sub.A)×100] of 5% or greater and smaller than 30%, wherein I.sub.A represents the sum of the peak intensities of the sialon species, and I.sub.21R represents the peak intensity of 21R-sialon, the ratio being calculated from the peak intensities of the sialon species obtained by using X-ray diffractometry.

A rotary tool comprises a cylindrical sleeve including an opening formed in an outer circumferential surface thereof providing fluid communication between a hollow interior of the sleeve and an environment surrounding the sleeve. The sleeve includes an axially extending flow passage formed therein terminating in a first fluid outlet formed in an open end of the sleeve disposed adjacent a cutting element of the rotary tool. The fluid outlet is configured to deliver a flow of a fluid toward the workpiece to cause chips formed during the machining operation to be directed away from the workpiece and out of the hollow interior of the sleeve through the opening formed in the outer circumferential surface thereof.

A combination cutting and burnishing orbital drilling tool may include an elongate tool body including a cutting end and extending along a longitudinal axis. The tool body may include a burnishing portion spaced from the cutting end and configured to induce residual stress in a side wall of a hole without removing material. The tool body may further include a cutting portion interposed between the cutting end and the burnishing portion. The cutting portion may be configured to remove material from a workpiece, thereby creating the hole, during an orbital drilling process.