Rotary tool cover

A rotary-tool cover comprising two side plates each having inwardly bent arcuate outer flanges, said flanges each having a width, said width being perpendicular to a radius extending from the center of the cover to the flange said side plates being connected after said bent outer flanges have been overlapped with each other, wherein a circumferential surface of the outer periphery of each of said bent outer flanges is bisected along said width so as to form two sectors and reduce the radius of one of the sectors by a thickness of said side plate, wherein the reduced sectors of each plate are overlapped by the non-reduced sectors, providing the cover with an outer flange portion with a thickness twice as large as that of each side plate, wherein the outer flanges thereby overlapped are welded together and the two side plates have the substantially same shape and size formed by press working using the same dies.