frictional fit restricting movement of the screw when it is subjected to vibration

1/4 x 2 Nailon™ Anchor Mushroom Zinc Plated (100)

2 1/4 F436 Flat Washer Plain

5/8-11 Drop-In Anchor Zinc Plated (25)

11/64 Cobalt Heavy Duty Jobber Drill Bit (12) 1/2 Hex Lag Screws Hot Dipped Galvanized frictional fit restricting movement of11 64 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.