To provide a method of manufacturing a shaft for a steering device, the shaft including a spline shaft part to be coupled with an input shaft, a stopper part to be coupled with an output shaft, and an intermediate shaft part that couples the spline shaft part with the stopper part. The method includes: a step of forming a hole part recessed in an axial direction from one end of a pillar-shaped material by forging; and a step of pressing the material in which the hole part has been formed into a die to perform drawing in a radial direction on a portion of the material at which the spline shaft part and the intermediate shaft part are formed, and prolonging a length along the axial direction of the hole part at the same time by forging.

To provide a method of manufacturing a shaft for a steering device, the shaft including a spline shaft part to be coupled with an input shaft, a stopper part to be coupled with an output shaft, and an intermediate shaft part that couples the spline shaft part with the stopper part. The method includes: a step of forming a hole part recessed in an axial direction from one end of a pillar-shaped material by forging; and a step of pressing the material in which the hole part has been formed into a die to perform drawing in a radial direction on a portion of the material at which the spline shaft part and the intermediate shaft part are formed, and prolonging a length along the axial direction of the hole part at the same time by forging.

A metal sleeve including a metal body which surrounds an inner channel running between a proximal and a distal opening. The inner channel has at least one groove set back into the metal body, running in the longitudinal direction of the inner channel and stepped on both sides by a distal and a proximal front edge. The proximal front edge of the groove is produced by impact extrusion.

A metal sleeve including a metal body which surrounds an inner channel running between a proximal and a distal opening. The inner channel has at least one groove set back into the metal body, running in the longitudinal direction of the inner channel and stepped on both sides by a distal and a proximal front edge. The proximal front edge of the groove is produced by impact extrusion.

In extrusion processing in which diameter reduction is performed by pressing a raw pipe having a core bar inserted therein into a die having a small inner diameter portion on its tip end side, a differential thickness pipe having a thick-walled portion at its tip end can be molded using a core bar having a small cross-section portion formed at its tip end. It is also possible to mold a differential thickness pipe having a thick-walled part at an intermediate axial position by using a raw pipe having a thin-walled portion at its tip end. For example, such a raw pipe can be molded by extrusion processing using a core bar having no small cross section portion at its tip end, prior to the above-described formation of the thick-walled portion. When higher dimensional accuracy is required, a so-called “counter punch” may be used in the formation of the thick-walled portion.

A material dispense tip includes an elongated hole in an elongated neck that extends from an input end of the neck to an output end of the neck. The hole at the output end of the neck has a first diameter. The output end of the neck is positioned against a die surface. A punch is inserted into the hole at the input end of the neck. An external force is applied to the neck to cause the output end of the neck to be deformed under compression by the die surface, to reduce the diameter of the hole at the output end of the neck from the first diameter to a second diameter that is less than the first diameter.

A material dispense tip includes an elongated hole in an elongated neck that extends from an input end of the neck to an output end of the neck. The hole at the output end of the neck has a first diameter. The output end of the neck is positioned against a die surface. A punch is inserted into the hole at the input end of the neck. An external force is applied to the neck to cause the output end of the neck to be deformed under compression by the die surface, to reduce the diameter of the hole at the output end of the neck from the first diameter to a second diameter that is less than the first diameter.

A pair of electrode lugs clamp a bar at side surfaces of the bar so as to be electrically connected to the bar. The electrode lugs respectively include a first contact portion and a second contact portion having different front-back lengths. The bar is clamped such that the first contact portion having a short front-back length L1 opposes a back end portion of the bar within a range of the second contact portion having a front-back length L2. The back end surface of the bar is brought into contact with and welded to a front end surface of a metal shell by resistance butt welding. Since the first contact portion of one lug is short and is close to the abutting surfaces, heat dissipation can be reduced and heat concentration can be increased.

A metal shell of a glow plug mounted on an engine head of a diesel engine and a method of manufacturing the same are disclosed. The metal shell has an improved multi-stage structure, which allows the metal shell to be easily manufactured regardless of overall length of the metal shell and allows a metal shell section fastened to the engine head and at least one of the other metal shell sections to have different material strengths, thereby increasing fastening strength of the metal shell to the engine head and preventing warpage of the metal shell while improving productivity while reducing manufacturing costs. The metal shell of a glow plug for diesel engines according to the invention includes a plurality of metal shell sections disposed in an axial direction of the glow plug and having different material strengths.

A metal shell of a glow plug mounted on an engine head of a diesel engine and a method of manufacturing the same are disclosed. The metal shell has an improved multi-stage structure, which allows the metal shell to be easily manufactured regardless of overall length of the metal shell and allows a metal shell section fastened to the engine head and at least one of the other metal shell sections to have different material strengths, thereby increasing fastening strength of the metal shell to the engine head and preventing warpage of the metal shell while improving productivity while reducing manufacturing costs. The metal shell of a glow plug for diesel engines according to the invention includes a plurality of metal shell sections disposed in an axial direction of the glow plug and having different material strengths.