The present disclosure provides a method for forging a gear capable of preventing burrs from being formed at an edge of the surface opposite to a direction in which a material in external teeth of the material is pushed. A first exemplary aspect is a method for moving the second punch along a tooth profile groove of the guide die to stack the material and the second punch in this order; and pushing the material and the second punch into a tooth profile groove of the tooth profile die in a stacked state to pass them therethrough, in which a tooth pressing part of the second punch covers at least an edge of a region where external teeth are formed on a surface of the material on the first punch side.

The present disclosure provides a method for manufacturing a gear capable of processing a projection formed on a tooth tip by shot peening while reducing time for manufacturing the gear. A method for manufacturing a gear includes: a process of hardening, by performing shot peening in which shot particles are jetted onto a tooth surface 1a of a gear base material, the tooth surface while applying residual stress to the tooth surface; a process of softening, by at least heating a tooth tip of the gear base material having the hardened tooth surface, the tooth tip; and a process of rotationally driving the gear base material having the softened tooth tip by engaging it with another gear.

The present disclosure provides a method for manufacturing a gear capable of processing a projection formed on a tooth tip by shot peening while reducing time for manufacturing the gear. A method for manufacturing a gear includes: a process of hardening, by performing shot peening in which shot particles are jetted onto a tooth surface 1a of a gear base material, the tooth surface while applying residual stress to the tooth surface; a process of softening, by at least heating a tooth tip of the gear base material having the hardened tooth surface, the tooth tip; and a process of rotationally driving the gear base material having the softened tooth tip by engaging it with another gear.

In a die for compressing and sizing a sintered body at straight portions, upper taper portions are provided on a die upper portion and a core rod upper portion, and the straight portions are provided at a die lower portion and a core rod lower portion. The die upper portion and the core rod upper portion have Young's moduli higher than the die lower portion and the core rod lower portion. The die upper portion and the core rod upper portion are made of materials having Young's moduli that are at least 50 GPa higher than that of the sintered body. The sintered body can be densified with a smaller ironing margin. Since the sintered body is ironed without being compressed, by the upper taper portions and the core rod upper portion having high Young's moduli, the die is prevented from breaking and being abraded due to ironing.

In a die for compressing and sizing a sintered body at straight portions, upper taper portions are provided on a die upper portion and a core rod upper portion, and the straight portions are provided at a die lower portion and a core rod lower portion. The die upper portion and the core rod upper portion have Young's moduli higher than the die lower portion and the core rod lower portion. The die upper portion and the core rod upper portion are made of materials having Young's moduli that are at least 50 GPa higher than that of the sintered body. The sintered body can be densified with a smaller ironing margin. Since the sintered body is ironed without being compressed, by the upper taper portions and the core rod upper portion having high Young's moduli, the die is prevented from breaking and being abraded due to ironing.

A mechanical structural component is a toothed component obtained by performing cold forging and carburizing treatment on a steel having a predetermined chemical composition, in prior austenite grains after the carburizing treatment, an area ratio of crystal grains of 50 m or less is 80% or more, and an area ratio of crystal grains exceeding 300 m is 10% or less, and a total helix deviation of teeth after the carburizing treatment satisfies Formula (1)
(B.sub.max/L)10.sup.35(1)
where B.sub.max is a maximum total helix deviation in all teeth in mm, and L is a face width in mm.

A mechanical structural component is a toothed component obtained by performing cold forging and carburizing treatment on a steel having a predetermined chemical composition, in prior austenite grains after the carburizing treatment, an area ratio of crystal grains of 50 m or less is 80% or more, and an area ratio of crystal grains exceeding 300 m is 10% or less, and a total helix deviation of teeth after the carburizing treatment satisfies Formula (1)
(B.sub.max/L)10.sup.35(1)
where B.sub.max is a maximum total helix deviation in all teeth in mm, and L is a face width in mm.

A method for forming an assembly having a housing and first and second components. The first and second components are movable relative to one another in the housing. The method includes: providing first and second workpieces; moving the first and second workpieces relative to one another in a predetermined manner that produces relative sliding contact between the first and second workpieces while performing a superfinishing operation on the first and second workpieces to form the first and second components, respectively, wherein the superfinishing operation does not comprise a lapping operation; and mounting the first and second components in the housing such that the first and second components are engaged to one another and are movable relative to one another in the predetermined manner.

A method for forming an assembly having a housing and first and second components. The first and second components are movable relative to one another in the housing. The method includes: providing first and second workpieces; moving the first and second workpieces relative to one another in a predetermined manner that produces relative sliding contact between the first and second workpieces while performing a superfinishing operation on the first and second workpieces to form the first and second components, respectively, wherein the superfinishing operation does not comprise a lapping operation; and mounting the first and second components in the housing such that the first and second components are engaged to one another and are movable relative to one another in the predetermined manner.

To provide a rotating member that allows formation of protrusions to be dug into an opposite surface with a simple configuration, and that can prevent a direction-dependent reduction of anti-slip effect and provide sufficient slip prevention in the direction of torque as well as in the radial direction, and a method of forming this rotating member. The rotating member has a boss and an anti-slip surface on at least one of both axial end faces of the boss. The anti-slip surface includes a plurality of crater-like depressions each having a peripheral protrusion. At least some of the plurality of crater-like depressions are arranged serially to form a plurality of crater chains.