Rigging shackles are made of which material in the screw pin or bolt pin styles?

• A. Carbon steel
• B. Alloy steel
• C. Stainless steel
• D. Cast iron

Answer: (B)

Rigging shackles must withstand high loads with reliability, and the screw pin or bolt pin styles rely on a metal that can be forged and heat-treated to achieve high yield and tensile strength plus good toughness. Alloy steel provides that ideal combination, delivering the strength needed to resist pulling apart and the toughness to absorb shocks without fracturing, while still offering workable weight and cost for most lifting applications. Cast iron is too brittle for dynamic lifting, stainless steel resists corrosion but is heavier and often not as strong for the same size and cost, and carbon steel, while strong, does not offer the higher strength and fatigue resistance that alloy steel provides.