Provided is a method of manufacturing an elbow, including: a first cutting step of cutting a material by relatively moving a cutting section of a cutting tool, which is formed of at least a part of a substantially spherical shape, along an inner side surface of the elbow to be finished in a direction from a first end surface to a second end surface of the material; and a second cutting step of cutting the material by relatively moving the cutting section along the inner side surface of the elbow to be finished in a direction from the second end surface to the first end surface of the material.

A production method for a ring-shaped part is provided with: an inner cutting step for reciprocating a first cutting blade in the radial direction D4 from a state of contact with the center of the thickness of one end 91a of a rotating cylindrical blank 91 and moving toward the other end 91b in the axial direction D1 to form a semicircular track while cutting the inner circumferential R1-side of the cylindrical blank 91; an outer cutting step before, after or simultaneously with the inner cutting step for reciprocating a second cutting blade in the radial direction D4 from a state of contact with the center of the thickness of the one end 91a of the rotating cylindrical blank 91 and moving toward the other end 91b in the axial direction D1 to form a semicircular track while cutting the outer circumferential R2-side of the cylindrical blank 91; and a separation step after the inner cutting step and the outer cutting step for cutting the portion 92 of the cylindrical blank 91, the inner circumferential R1-side and the outer circumferential R2-side of which have been cut, from the remainder 93 of the cylindrical blank 91 to obtain a ring-shaped part 94 with a roughly circular cross-section.

Provided is a method of manufacturing an elbow, including: a first cutting step of cutting a material by relatively moving a cutting section of a cutting tool, which is formed of at least a part of a substantially spherical shape, along an inner side surface of the elbow to be finished in a direction from a first end surface to a second end surface of the material; and a second cutting step of cutting the material by relatively moving the cutting section along the inner side surface of the elbow to be finished in a direction from the second end surface to the first end surface of the material.

A production method for a ring-shaped part is provided with: an inner cutting step for reciprocating a first cutting blade in the radial direction D4 from a state of contact with the center of the thickness of one end 91a of a rotating cylindrical blank 91 and moving toward the other end 91b in the axial direction D1 to form a semicircular track while cutting the inner circumferential R1-side of the cylindrical blank 91; an outer cutting step before, after or simultaneously with the inner cutting step for reciprocating a second cutting blade in the radial direction D4 from a state of contact with the center of the thickness of the one end 91a of the rotating cylindrical blank 91 and moving toward the other end 91b in the axial direction D1 to form a semicircular track while cutting the outer circumferential R2-side of the cylindrical blank 91; and a separation step after the inner cutting step and the outer cutting step for cutting the portion 92 of the cylindrical blank 91, the inner circumferential R1-side and the outer circumferential R2-side of which have been cut, from the remainder 93 of the cylindrical blank 91 to obtain a ring-shaped part 94 with a roughly circular cross-section.

The invention relates to apparatus for use with a drill bit which is driven to rotate so as to form a hole in a workpiece with which the same is contacted. The apparatus includes guide means with which the drill bit is located and a body with which the workpiece is located and said guide means is movable with respect to the body to cause the drill bit to be advanced along a path which includes an arc portion and, as it is driven to rotate, move into the workpiece to form said hole and allow the hole to be formed in a guided manner with greater accuracy.