Abstract: The present invention provides a base substrate for epitaxial diamond film capable of epitaxially growing a large area of high quality diamond, having a diameter of 1 inch (2.5 cm) or more, on an iridium base by using the CVD method, a method for producing the base substrate for epitaxial diamond film, an epitaxial diamond film produced with the base substrate for epitaxial diamond film and a method for producing the epitaxial diamond film. An iridium (Ir) film is formed by epitaxial growth on a single crystal magnesium oxide (MgO) substrate or a single crystal sapphire (?-Al2O3) substrate by means of a vacuum deposition method or a sputtering method, and a bias nucleus generation process of forming epitaxial diamond nuclei is applied to the surface of the iridium (Ir) base formed as a film by exposing an ion-containing direct current plasma to the surface of the iridium (Ir) base formed as a film.

Abstract: There is provided a multilayer substrate comprising, at least, a single crystal MgO substrate, an iridium (Ir) film heteroepitaxially grown on the MgO substrate, a diamond film vapor-deposited on the Ir film, wherein crystallinity of the Ir film is that a full width at half maximum (FWHM) of a diffracted intensity peak in 2 ?=46.5° or 2?=47.3° attributed to Ir (200) analyzed by X-ray diffraction method with a wavelength of ?=1.54 ? is 0.40° or less. Thereby, there is provided a multilayer substrate that is delamination-proof at the respective interfaces between the MgO substrate and the Ir film and between the Ir film and the diamond film, and, particularly, that has a single crystal diamond film of a large area as a continuous film.

Abstract: A cutting tap comprises a threaded portion including a lead whose thread diameter gradually decreases toward a front end of the lead, a complete thread portion continued from the lead, and four flutes arranged at equal intervals in a circumferential direction. In the cutting tap, a first cutting edge portion for processing a prepared hole is formed at a front end surface of the lead, and a second cutting edge portion for finishing a minor diameter of an internal thread is formed in a part of an outer periphery of the complete thread portion, the second cutting edge portion being one or more pitches long. The cutting tap can perform processing of a prepared hole, tapping, and finishing of a minor diameter by a single step, and can also perform tapping even if a prepared hole for an internal thread is a blind hole or the like and does not have enough space.