Specifications include, but are not limited to: 1.0 BLADE 1.1 Blades shall be flat hot-rolled finished steel SAE 1020 of domestic manufacture. 1.2 Punching shall be 11/16" square holes to receive 5/8" diameter carriage bolts. Location and spacing of the holes shall be as shown on the attached drawings. 1.3 The groove for the carbide inserts shall be milled in the center of the blade edge. 1.4 Center of holes shall be in line within 1/32" of established centerline. 2.0 TUNGSTEN CARBIDE INSERTS 2.1 The inserts shall be WC grade of tungsten carbide with 11% to 12% cobalt content. Density: 14.1 minimum to 14.6 maximum. Hardness: 87.5 minimum to 89.0 maximum Rockwell "A" Scale. Transverse Rupture Strength (P.S.I.): 350,000 minimum. Porosity: (ASTM B276-79) A 06 B 00 C 00 2.3 Insert Design. The inserts shall be trapezoidal in shape to the following dimensions: Height: .750 + .005 (Long side) Width: .365 + .010 Length: 1 in. nominal Bottom Angle: 25 degrees with a nose radius of 1/16" minimum. 2.4 A metallurgical evaluation of the carbide insert shall show no evidence of cross grade contamination. Evaluation to be based on a photo micrograph of a polished and etched specimen at 500X magnification. 3.0 BRAZING 3.1 The brazing material shall be a high strength alloy type. The braze shear strength to be 30,000 psi minimum. 3.2 The tungsten carbide inserts shall be positioned in the milled groove at .010 between the inserts the entire length of each cutting edge section. 3.3 The inserts shall be brazed on all sides consistent with sound brazing practice with no evidence of voids or use of shims. 3.4 Each blade section to contain one insert, one-inch nominal length for each inch of blade section length. Reference 2.3.
