Hoist rings are load-centering eyebolts. They are designed to be rigged from the center or the side and may pivot or swivel. Some hoist rings connect directly to webbing, chain, or shackles. Others have a hook-end rather than a standard bail, eye, or ring. There are three basic types of hoist rings: center-pull hoist rings, side-pull hoist rings, and screw-mount lifting rings. Center-pull hoist rings are designed to be rigged from the center and should not be set up to be pulled from the side. Side-pull hoist rings are designed to be rigged from the side and should not be set up to be pulled from the center. Screw-mount lifting rings are hoist rings with a fixed base. They have mounting holes for screws. In terms of movement, pivoting hoist rings have an eye that is designed to pivot 180°. Swiveling hoist rings are designed to swivel 360°. Product specifications for hoist rings include maximum load capacity, threaded length, overall bail length, overall bail width, bail radius, bail thickness, and weight. The bail size is defined as the bail diameter for round-eye hoist rings, and the bail width for oval or triangular hoist rings.
Hoist rings differ in terms of material and finish. Metallic hoist rings can be made of aluminum, brass, bronze, steel, hardened steel, stainless steel, titanium, or proprietary alloys. Aluminum is lighter than steel, but not as strong. Brass and silicon bronze are common copper-base alloys. Many different grades of carbon steel and alloy steel are used as fastener materials. Stainless steel may not require anti-corrosion coatings, but cannot be hardened to the same degree as carbon steels. Titanium, a metal that is used widely in the aerospace industry, is suitable for specialized applications. In terms of finish, hoist rings are often anodized, galvanized, or plated with gold, silver, tin, or zinc. Black oxide is a hoist ring coating that causes virtually no dimensional change. Phosphate coatings provide corrosion resistance and a better surface for the adhesion of primers and paints. Hoist rings with zinc chromate finishes are also available.
Thread sizes for hoist rings are measured in English units such as inches (in) or metric units such as millimeters (mm). Measurements for inch-based hoist rings include: 1/4, 5/16, 3/8, 7/17, 1/2, 5/8, 3/4, 7/8, 1, 1 1/8, 1 1/4, 1 3/8, 1 1/2, 1 3/4, 2, 2 1/4, 2 1/2, and 2 3/4 inches. Fasteners designated as #16, #18, #20, #24 hoist rings are also available. Designations for metric hoist rings include: M6, M8, M10, M12, M14, M16, M18, M20, M22, M24, M25, M26, M27, M28, M30, M32, M33, M35, M36, M38, M40, M42, M48, M56, and M54. As a rule, the numbers which follow the letter “M” indicate the number of millimeters in diameter. For example, an M6 hoist ring is 6 mm in diameter.