Abstract: One object of the present invention is to provide a cutting tool excellent in strength and wear resistance. The cutting tool has a cutting blade formed using a highly hard diamond polycrystalline body made substantially only of diamond and produced by directly converting a raw material composition including a non-diamond type carbon material into diamond and sintering the diamond at an ultra high pressure and an ultra high temperature without adding a sintering aid or a catalyst, the polycrystalline body having a mixed construction including fine-grained diamond crystals with a maximum grain size of less than or equal to 100 nm and an average grain size of less than or equal to 50 nm and plate-like or particulate coarse-grained diamond crystals with a minimum grain size of greater than or equal to 50 nm and a maximum grain size of less than or equal to 10000 nm.

Abstract: A mono crystalline diamond cutting tool is provided which can perform ultra precision machining on a crystalline material or a hard and brittle material with good swarf discharge and reduced cutting resistance to improve a precision of a cut surface, and has less wear or microchipping of a cutting edge and thus achieves long life. A tip having a cutting edge ridge in a rounded shape at a front end is provided, and a portion of the cutting edge ridge serving at least as a cutting edge is formed to have constant roundness by intersecting a first conical surface as a rake face with a second conical surface as a flank. The cutting edge ridge is rounded with a radius of less than 100 nm, the first conical surface has a width of 1 to 5 ?m, and a swarf release face substantially perpendicular to a cutting direction is provided in a portion on a side of the first conical surface opposite a line of the cutting edge ridge.

Abstract: A mono crystalline diamond cutting tool is provided which can perform ultra precision machining on a crystalline material or a hard and brittle material with good swarf discharge and reduced cutting resistance to improve a precision of a cut surface, and has less wear or microchipping of a cutting edge and thus achieves long life. A tip having a cutting edge ridge in a rounded shape at a front end is provided, and a portion of the cutting edge ridge serving at least as a cutting edge is formed to have constant roundness by intersecting a first conical surface as a rake face with a second conical surface as a flank. The cutting edge ridge is rounded with a radius of less than 100 nm, the first conical surface has a width of 1 to 5 ?m, and a swarf release face substantially perpendicular to a cutting direction is provided in a portion on a side of the first conical surface opposite a line of the cutting edge ridge.