the hardness rating is HRC 24-35

Open-end button head rivets offer the broadest selection of sizes available

Screws with a diameter over 1 ½ inches have a hardness rating of HRB 95 - HRC 35

1/4 x 2 Flat Split Drive Anchor Zinc Plated (100)

43/64 x 6 Reduced Shank Drill Bit (1/2 Shank)

1/16 Cobalt Heavy Duty Jobber Drill Bit (12) Flat Washers Silicon Bronze the hardness rating is HRC1 16 Cobalt Heavy Duty Jobber Drill Bit . Heavy duty construction made to Type J aircraft specifications. Used for drilling holes in hard, tough materials such as stainless steel, titanium, high temperature and high strength alloys. High red hardness of cobalt permits speeds 30% greater than standard heavy duty split point (HSS) drills.