Abstract: Improvements in a method of making a poly-V pulley from a metal plate which has V-shaped poly-V grooves formed in a cylindrical flange wall of a cup-shaped blank, by the application of pressing, compression and finishing processes to the blank. More particularly, the improvements reside in the compression process in which the opening end of the flange wall of a cup-shaped blank is fittingly held by a fitting groove which is formed in an upper peripheral edge of a lower rotary pressing form, the groove having a slope with a predetermined upward inclination in the radially inward direction toward the center of the form. Auxiliary rollers are pressed into groove valleys of the corrugated wall of the blank, and the blank is then axially compressed while rotating the blank, thereby converting the corrugated wall into a grooved wall having therein a series of V-shaped crests and valleys.

Abstract: A method for manufacturing a poly-V pulley comprising pre-forming the flange wall of a cup-shaped blank to have a corrugated cross section having a series of valleys formed around the outer circumference thereof, axially compressing the corrugated flange wall of the blank, and pressing a rotary forming roller against valleys formed around the outer circumference of the flange wall to form each of valleys to a predetermined V-groove. The axially compressing process is carried out keeping respective outer circumference of axially movable auxiliary forming rollers inserted into their corresponding valleys formed around the outer circumference of the flange wall of the blank.