A single station hemming device for hemming the upstanding peripheral flange of an outer element to overlie the periphery of an inner element to thereby join the outer element to the inner element. The hemming device has a series of hemming tools positioned end-to-end around the periphery of the outer element, each hemming tool being actuated in unison by a single motor to simultaneously hem the peripheral flange of the outer part. Each hemming tool is cam operated through a system of links by a single actuator to move in a first arcuate direction generally transversely of the flange to do a first stage hemming operation of about 35.degree.-55.degree.; then in a second arcuate direction to lift it above the flange and then in a third arcuate direction generally parallel to the original orientation of the flange to complete the remaining approximately 55.degree.-35.degree. of hemming of the flange. One or more of the hemming tools can be provided with a reciprocable piercing tool to pierce a tab of the peripheral flange of the outer element and an adjacent surface of a raised pad of the inner element, after conclusion of the hemming operation, to interlock the outer element and the inner element together.