Cutting tool sharpener

An apparatus for sharpening a cutting tool having opposing first and second side surfaces and a cutting edge therebetween, the apparatus comprising:

• a plurality of spaced apart rollers;
• a flexible abrasive belt having an abrasive top surface and an opposing backing surface, the flexible abrasive belt routed around the plurality of rollers to form a triangular path defining respective first and second planar extents tangential to and on opposing sides of a first roller of the plurality of rollers, each of the first and second planar extents symmetric with respect to a centerline passing through a central axis about which the first roller rotates, the central axis bisecting an overall angle between the first and second planar extents;
• a motor adapted to drive the flexible abrasive belt in a selected direction along the triangular path so that the belt moves toward the first roller along the first planar extent and moves away from the first roller along the second planar extent;
• a sharpening guide assembly secured adjacent the flexible abrasive belt and the first roller comprising a first guide slot adjacent the first planar extent of the flexible abrasive belt and a second guide slot adjacent the second planar extent of the flexible abrasive belt, wherein the first and second guide slots further comprise first and second cutting edge guide surfaces adapted to contactingly engage the cutting edge of the cutting tool during presentation of the respective first and second sides of the cutting tool against first and second cutting edge guide surfaces, first and second cutting edge guide surfaces are symmetric about the centerline of the first roller so that each of the first and second side surfaces are disposed at a common, selected acute angle with respect to the first and second planar extents of the flexible abrasive belt to support the opposing first and second side surfaces of the cutting tool as the cutting edge of the cutting tool is contactingly presented against the respective first and second planar extents, wherein the opposing backing surface of the flexible abrasive belt is not mechanically engaged by any support member opposite the cutting edge as the cutting tool is respectively presented against the first and second side surfaces.

A method for sharpening a cutting tool having opposing first and second side surfaces and a cutting edge therebetween, the method comprising:

• installing a first flexible abrasive belt along a triangular path about a plurality of spaced-apart rollers, the first flexible abrasive belt having a first linear stiffness, the triangular path defining respective first and second planar extents tangential to and on opposing sides of a first roller of the plurality of rollers, each of the first and second planar extents symmetric with respect to a centerline passing through a central axis about which the first roller rotates, the central axis bisecting an overall angle between the first and second planar extents;
• driving the first flexible abrasive belt along the triangular path in a selected direction, wherein a tensioner assembly applies a bias force to at least one of the rollers to establish a tension in the driven first flexible abrasive belt and maintain said first and second planar extents;
• providing a sharpening guide adjacent the flexible abrasive belt, the sharpening guide comprising a first guide slot adjacent the first planar extent and a second guide slot adjacent the second planar extent;
• wherein the guide slots are on both sides of the centerline;
• using the first guide slot of the sharpening guide to present the first side of the cutting tool against the first extent of the first flexible abrasive belt driven in a relative direction away from the first roller to induce torsion of the driven first flexible abrasive belt out of the tangential plane and to concurrently induce bending of the flexible belt at a first radius of curvature determined in relation to the first linear stiffness to form a first convex shape on the first side of the cutting tool at said first radius of curvature, wherein the first guide slot establishes a selected angle of the cutting tool relative to a centerline that bisects an overall angle between the first and second planar extents;
• and
• using the second guide slot of the sharpening guide to present the opposing second side of the cutting tool against the second extent of the driven first flexible abrasive belt driven in a relative direction toward the first roller to induce torsion of the driven first flexible abrasive belt out of the tangential plane and to concurrently induce bending of the flexible abrasive belt at the first radius of curvature to form a first convex shape on the second side of the cutting tool at said first radius of curvature, wherein the second guide slot maintains the cutting tool at the selected angle.