Patent ID: 8100194

Claim:
An apparatus comprising: a metal disc that is generally circular and has an outer periphery; a plurality of notches disposed in the outer periphery of the disc; each of the plurality of notches tapering from a predetermined thickness on a radial inside to a thinner generally sharpened edge at the radially outermost part thereof; each notch having a forward end that is sharper than a rearward end; the metal disc having one side disposed along a first plane and an opposite side disposed along a second plane; an imaginary third plane extending perpendicular to at least one of the first and second planes and through a forward end of one of the notches, a first point being located where the third plane intersects the first plane and a second point being located where the third plane intersects the second plane; an imaginary fourth plane extending perpendicular to at least one of the first and second planes and through a rearward end of said one of the notches, a third point being located where the fourth plane intersects the first plane and a fourth point being located where the fourth plane intersects the second plane; and wherein the distance between the first and second point is farther than the distance between the third and fourth points.