Proof Load testing. Iron nut M12 and with thread pitch 1.75 ASTM F606/F606M Item 4.2 ASTM A962/A962M Item 11.1 ISO 3506 2 Item 10.1 ISO 898-2 Item 9.1 Proof Load testing. Zinc Plated Iron Nut M20 and with thread pitch 2.5   Proof Load testing. Zinc Plated Iron Nut 3/4 of 10 threads per inch and whitworth pitch