Master Links in Rigging: Types, Grades and How to Select

What Is a Master Link in Rigging?

A master link is the central gathering component in a multi-leg sling assembly. It collects the upper ends of two, three, or four sling legs and provides a single load-rated connection point for the crane hook or hoist hook. The master link is what the crane hook seats into - everything below it is the sling assembly, and everything above it is the crane.

Master links are forged from alloy steel and heat treated to the same grade system as the chain slings they are used with. Grade 80 and Grade 100 are the two grades used in industrial lifting. The grade of the master link must match the grade of the chain sling assembly - mixing grades creates a capacity limitation at the lower-grade component.

What Does a Master Link Do?

In a multi-leg chain sling assembly, each sling leg has a hook on the load end that attaches to a pad eye, lifting lug, or attachment point on the load. The upper end of each leg connects to the master link. The master link gathers all legs into a single point that fits the crane hook. The crane picks the load by lifting the master link, which carries the combined load from all legs.

The master link must be rated for the total load from all legs at the sling angle being used. A two-leg chain sling at 60 degrees from vertical does not carry twice the single-leg WLL - sling angle reduces the effective capacity of each leg. The master link selection must account for the actual load the link carries at the configured angle.

Types of Master Links

Oblong Master Links

The standard configuration in industrial chain sling assemblies. The oblong body provides a wide opening that crane hooks seat cleanly into and accommodates multiple sling leg connections without crowding. Oblong master links are stocked in Grade 80 and Grade 100 across a range of chain sizes. The Crosby A-342 (Grade 80) and A-347F (Grade 100) are the standard oblong master links stocked at Holloway Houston.

Pear-Shaped Master Links

The pear-shaped body provides a larger opening on the crane hook end for hooks that are too large to seat in a standard oblong link, while the narrower section at the bottom accommodates sling leg connections. Pear-shaped master links are specified where the overhead crane has a large hook that does not fit the standard oblong opening. Available in Grade 80 and Grade 100.

Adjustable Master Links

Adjustable links allow the effective WLL of the assembly to be modified by changing the number of active legs in the assembly. Used in multi-leg assemblies where the lift configuration varies by job and the rigger needs to adjust how many legs are carrying load.

Master Link Assemblies

Master link assemblies combine an oblong master link with attached sub-links or sling hooks for each leg - the complete crane-end component for a multi-leg chain sling kit. These arrive ready to accept the chain sling legs without additional connecting hardware. Available as two, three, and four-leg configurations.

Grade Selection

Master link grade must match or exceed the grade of the other components in the sling assembly. Using a lower-grade master link in a higher-grade assembly makes the master link the limiting component and defeats the purpose of upgrading to higher-grade chain.

Inspection

Master links are inspected per ASME B30.9 before each use and at periodic intervals. Remove from service if any of the following are observed:

• Cracks or gouges in the link body
• Deformation of the oval shape
• Wear at the bearing surfaces where the hook or sling legs contact the link
• Elongation beyond original dimensions indicating stretch
• Corrosion reducing the cross-sectional area
• WLL markings that are no longer legible

A master link that has been subjected to shock loading - a sudden load application or dropped load event - must be removed from service and inspected by qualified personnel before returning to use, even if no visible damage is present.