Seymour S500 Industrial bores different size holes by adjusting the yolk. Yoke locked into position by tightening yoke locking bolt. Heavy-gauge alloy steel blades riveted to malleable iron adjustable yoke. Steel tee welded to 3/4 In. diameter, high-tensile, steel tubular shaft. Boring sizes: 6 In., 7 In., and 8 In. Overall dimensions: 21 In. W. x 46.5 In. H. x 3/4 In. Dia.