On diameters over 1 inch to 1 1/2 hardness will range from HRC 19-30

27/64 Heavy Duty Jobber Drill Bit

7/16-14 x 1 1/2 Hex Tap Bolt 18-8 (A2) Stainless Steel

3 USS Flat Washer Zinc Plated

7/8 x 12 ITM SDS Plus Hammer Drill Bit

8 x 1 Simpson Flat-Head Marine Screw - Phillips Drive 316 SS - Box (100) 1-8 Grade 5 Hex Cap Screws Zinc Plated On diameters over 1 inch8 x 1 Simpson Flat Head Marine Screw Phillips Drive 316 SS Box (100) . Marine screws bite and hold fast in fiberglass, plywood and wood substitute materials Use for projects exposed to harsh marine or many chemically caustic conditions Ideal for applying trim, rub rail and molding to fiberglass boat hulls Extra sharp points speed screw starts during assembly Specially engineered, high low thread form incorporates indentations ("teeth") that cut easily