Abstract: The present disclosure improves the machining conditions and enhances the quality of machined surfaces, particularly in cutting off and grooving machining when the projection amount of a plate-like member is large. A blade, which is a plate-like member having a polygonal shape and used for cutting machining, includes: a plurality of insert pockets; and recess portions formed by partial cutting corresponding to insert pockets respectively. A holder includes: a holder main portion; and a support portion with which a part of the recess portion formed in the blade contacts. The holder is configured in which the blade can be installed in a state where the part of the recess portion can contact with the support portion.

Abstract: A cutting edge tip of a cubic boron nitride sintered body has improved joint strength to a substrate of a cemented carbide. A cutting edge tip of a cubic boron nitride sintered body has improved crater wear resistance. A tool 10 of the present invention includes a substrate 12 of a cemented carbide and a cutting edge tip 14 of a cubic boron nitride sintered body joined to the substrate 12. The cutting edge tip 14 has a thickness covering an upper surface 12a to a lower surface 12b of the substrate 12. The cubic boron nitride sintered body contains 50 volume % or more and 95 volume % or less of cubic boron nitride and 5 volume % or more and 50 volume % or less of a binder phase. The cubic boron nitride has an average grain size of 1.0 ?m or more and 6.0 ?m or less.

Abstract: A cutting edge tip of a cubic boron nitride sintered body has improved joint strength to a substrate of a cemented carbide. A cutting edge tip of a cubic boron nitride sintered body has improved crater wear resistance. A tool 10 of the present invention includes a substrate 12 of a cemented carbide and a cutting edge tip 14 of a cubic boron nitride sintered body joined to the substrate 12. The cutting edge tip 14 has a thickness covering an upper surface 12a to a lower surface 12b of the substrate 12. The cubic boron nitride sintered body contains 50 volume % or more and 95 volume % or less of cubic boron nitride and 5 volume % or more and 50 volume % or less of a binder phase. The cubic boron nitride has an average grain size of 1.0 ?m or more and 6.0 ?m or less.