US Patent 7052385 Self-aligning blade angle guide

A device for use in the manual sharpening of arrow broadheads, razor blades and the like includes a unique symmetrical clamp and axle assembly having interchangeable, matched pairs of special purpose jaw members for gripping blades of differing configurations. When coupled to the frame, the clamp and axle assembly is freely rotatable, and this free rotation automatically aligns the length of the edge of the blade with the surface of a whetstone. Additionally these rotational and self-aligning capability enable the user to service both sides of the blade's edge with a single blade clamping operation, by manually rotating the clamp 180 degrees between passes along the surface of the whetstone.