A precision forging method includes arranging a metal material in a die cavity so that a distal end surface of a wall portion of the metal material is opposed toward a stopper and a bottom portion of the metal material is opposed toward a punch. Further, the precision forging method includes moving the punch, which includes a cutting blade on an edge of a working end surface, in the die cavity to cut part of the wall portion thickness-wise with the cutting blade and cause shear deformation in the cut portion.

The present invention provides a ring gear and a gear reduction device. The ring gear includes a one-piece annular body made from powder metallurgy material, and a first ring gear part and a second ring gear part formed on a surface of the annular body. The first ring gear part and the second ring gear part are arranged along an axial direction of the annular body. The ring gear has a density that is less than 92% of its theoretical density and in the range of 6.0 to 8.0 grams per cubic centimeter. The present invention further provides a mold for manufacturing the ring gear. The ring gear of the present invention includes two ring gears integrally formed at once, and the two ring gears have improved concentricity.

The present invention provides a ring gear and a gear reduction device. The ring gear includes a one-piece annular body made from powder metallurgy material, and a first ring gear part and a second ring gear part formed on a surface of the annular body. The first ring gear part and the second ring gear part are arranged along an axial direction of the annular body. The ring gear has a density that is less than 92% of its theoretical density and in the range of 6.0 to 8.0 grams per cubic centimeter. The present invention further provides a mold for manufacturing the ring gear. The ring gear of the present invention includes two ring gears integrally formed at once, and the two ring gears have improved concentricity.

A method of making a worm gear. The method includes forming a gear blank having a plurality of individual lugs formed about an outer circumferential edge of said blank to facilitate a uniform flow of a material around said plurality of individual lugs. The method also includes molding said material around said plurality of individual lugs to form a ring.

A method of making a worm gear. The method includes forming a gear blank having a plurality of individual lugs formed about an outer circumferential edge of said blank to facilitate a uniform flow of a material around said plurality of individual lugs. The method also includes molding said material around said plurality of individual lugs to form a ring.

A method for producing a gearwheel having an axis of rotation and a tooth system. The teeth have an axial undercut on the tooth flank sides thereof. A blank is provided having a tooth system, wherein the teeth of the tooth system are provided so as to be tilted relative to the axis of rotation such that a forming tool can advance substantially fully into the tooth flank sides of the teeth through an axial linear motion along the axis of rotation. A preliminary form of the at least one axial undercut can be provided on the tooth flank sides. A first axial forming operation is performed in the form of a first axial forging blow via which a preliminary form of the at least one axial undercut is introduced on the tooth flank sides or an already existing preliminary form of an axial undercut is sized for accuracy.

A method for producing a gearwheel having an axis of rotation and a tooth system. The teeth have an axial undercut on the tooth flank sides thereof. A blank is provided having a tooth system, wherein the teeth of the tooth system are provided so as to be tilted relative to the axis of rotation such that a forming tool can advance substantially fully into the tooth flank sides of the teeth through an axial linear motion along the axis of rotation. A preliminary form of the at least one axial undercut can be provided on the tooth flank sides. A first axial forming operation is performed in the form of a first axial forging blow via which a preliminary form of the at least one axial undercut is introduced on the tooth flank sides or an already existing preliminary form of an axial undercut is sized for accuracy.

A method of making a bicycle sprocket having a rotational center axis basically includes providing an annular portion and forming a first tooth and a second tooth. The annular portion is made of a base material and has a plurality of teeth. At least one of the teeth is processed to form a first tooth, and at least one other of the teeth is processed to form a second tooth. The first tooth has a first axial chain engaging width that is smaller than a first axial spacing of an outer link of a bicycle chain and larger than a second axial spacing of an inner link that is coupled to an outer link. The second tooth is formed to have a second axial chain engaging width that is smaller than the second axial spacing. The second tooth is formed by deforming the base material.

A method of making a bicycle sprocket having a rotational center axis basically includes providing an annular portion and forming a first tooth and a second tooth. The annular portion is made of a base material and has a plurality of teeth. At least one of the teeth is processed to form a first tooth, and at least one other of the teeth is processed to form a second tooth. The first tooth has a first axial chain engaging width that is smaller than a first axial spacing of an outer link of a bicycle chain and larger than a second axial spacing of an inner link that is coupled to an outer link. The second tooth is formed to have a second axial chain engaging width that is smaller than the second axial spacing. The second tooth is formed by deforming the base material.

A spline-processing method is used for a wheel bearing. The wheel bearing includes outer and inner members. The inner member has formed on its inner periphery an interference-defined spline having a guide spline formed at an inboard-side end portion thereof. An intermediate component of the inner member includes a spline-formation inner peripheral surface having the interference-defined spline and the guide spline formed thereon, and a relief portion, which is formed on an outboard side with respect to the spline-formation inner peripheral surface, and has a diameter larger than that of the spline-formation inner peripheral surface. A punch used for the spline processing includes an integrated spline punch having an interference-defined spline forming surface to form the interference-defined spline, and a guide spline forming surface to form the guide spline. The integrated spline punch presses the spline-formation inner peripheral surface to form the interference-defined spline and the guide spline.