Method of forming a boss on a plate-like metallic blank, and method of forming a pulley from a metallic plate

A method of forming a pulley from a metallic plate having a case-like boss projecting from one lateral side of the blank, said pulley having V-grooves formed in an outer peripheral wall portion of the blank,

• the method comprising the steps of:
• curving a plate-like metallic blank such that the blank is convex in a direction in which the boss is adapted to project, the curved blank having a top, an arcuate portion and an outer peripheral edge portion;
• punching a hole in the top of the curved blank;
• bending the arcuate portion of the curved blank between the outer peripheral edge portion and a peripheral portion of the hole in the curved blank in the direction opposite to the convex direction thereof with the outer peripheral edge portion of the curved blank restrained from extending radially outwardly, so that a flat portion and a case-like boss are formed;
• thickening an outer peripheral portion of the curved blank to form the outer peripheral wall portion by pressing the flat portion of the curved blank after said bending step, in the thickness direction thereof;
• and
• forming V-grooves in the thickened outer peripheral wall portion.

A method of forming a pulley made of a metallic plate having a case-like boss projecting from one lateral side of the blank, said pulley having V-grooves formed in an outer peripheral wall portion of the blank,

• the method comprising the steps of:
• curving a plate-like metallic blank such that the curved blank is convex in a direction in which the boss is adapted to project, the curved blank having a top, an arcuate portion and an outer peripheral edge portion;
• punching a hole in the top of the curved blank;
• bending the arcuate portion of the curved blank between the outer peripheral edge portion and a peripheral portion of the hole in the curved blank in the direction opposite to the convex direction thereof with the outer peripheral edge portion of the blank restrained from extending radially outwardly, so that a flat portion and a case-like boss are formed;
• pressing the flat portion of the curved blank after said bending step, in the thickness direction thereof such that the flat portion is so extended as to have a predetermined outer diameter;
• forming the peripheral wall portion on the curved blank by bending the outer end side of the flat portion as pressed, in one direction along the axis of rotation of the pulley;
• and
• forming V-grooves in the peripheral wall portion.