Wire Rope Sling Connections and Hitches

Use a thimble to protect sling and increase D/d (the ratio of the diameter of eye to the diameter of wire rope).
Do not force eyes over hardware. Make sure that the width of hook or diameter of shackle is no bigger than 1/2 the length of the eye.

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	A choker hitch has 75% of the capacity of a single leg only if the corners are softened and the horizontal angle is greater than 30 degrees. Use blocks to prevent angles less than 30 degrees.
	Angle of Choke Capacity 120°-180° 75% of Vertical 90°-109° 65% of Vertical 80°-89° 55% of Vertical 30°-59° 40% of Vertical

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A basket hitch has twice the capacity of a single leg only if legs of sling are vertical.

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Understanding the basics of the Rigging Triangle will help riggers answer many key questions about rigging with wire rope bridles. The included angle is checked for proper connection at the load hook or masterlink. The horizontal sling angles determine the loads placed on each leg of the sling. The horizontal sling angles will be equal only if sling lengths are the same length and the Center Of Gravity(COG) is in the middle of the pick points.

THE RIGGING TRIANGLE

The Rigging Triangle basic facts :

• Angular or side loading can occur at load
• Sling length affects horizontal sling angle
• 60 degrees sling angle is best, 30 degrees is worst choice
• As the sling angle becomes smaller, the load is "crushed" and sling work harder
• The fittings at load connection see the same load as the sling
• As the horizontal sling angle angle becomes smaller, significant horizontal forces are developed. These horizontal forces add to the sling load, tend to crush the work piece, and can cause buckling.

A horizontal sling angle of 60 degrees or greater is the preferred choice and is achieved when the sling length is equal to or greater than the distance across the pick points. (This rule of thumb only works when the slings are same length and C.O.G. is in middle of two pick points).

THE LOAD MULTIPLIER EFFECT

Sling Angle Degrees Load Angle Factor = L / H 90 1.000 60 1.155 50 1.305 45 1.414 30 2.000 Load on each leg of sling = (load ÷ 2) x load angle factor

ANSI B30.9 recommends against the use of a horizontal sling angle smaller than 30 degrees.

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Triple Leg Slings have 50% more capacity than double leg slings (at the same sling angle) only if the Center Of Gravity is in the center of connection points and legs are adjusted proper (they must have an equal share of the load).

Quad (4-legged) slings offer improved stability but provide increased capacity only if the legs share an equal share of the load.

A Chart of Wire Rope Sling Capacities of various hitches are as follow :

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7. Reference Material

a. Trigonometry Table is available at

b. Metric Conversion Calculator is available at