Developing roller manufacturing method, developing roller, developing device, and image forming apparatus

A method of manufacturing a developing roller, comprising:

• a first rolling process for forming a first inclined groove which is continuous in a helical shape, by rotating a first die having blades inclined with respect to an axial direction and a circumferential direction, and a non-bladed die in the same direction, and feeding an unprocessed developing roller between the first die and the non-bladed die while rotating the developing roller in the direction opposite to the rotation direction of the first die and the non-bladed die and applying a working pressure to the developing roller;
• and
• a second rolling process for forming a second inclined groove which is continuous in a helical shape and intersects with the first inclined groove, by rotating a second die having blades inclined with respect to an axial direction and a circumferential direction in the direction opposite to that of the first die, and the non-bladed die in the same direction opposite to that in the first rolling process, and feeding the developing roller on which the first inclined groove has been formed, between the second die and the non-bladed die while rotating the developing roller in the direction opposite to that in the first rolling process and applying a working pressure to the developing roller,
• wherein burrs are formed on the ridge lines of two sides which face any one side of the axial direction of the developing roller, in a quadrangle convex portion surrounded by the first inclined groove and the second inclined groove.