Machinery eye bolts are one of the most common types of rigging hardware used for lifting or securing machinery and equipment. Like slings, sling hooks, and shackles, eye bolts also come in various designs and configurations, made of different materials, like 304 stainless steel and zinc-plated high-carbon steel.
While they're widely utilized in industrial applications, eye bolts are also one of the most frequently misinterpreted and misused pieces of hardware. Their misuse and overuse are unfortunately widespread, and given their importance in overhead lifting, abusing them raises the danger of failure, equipment damage, and injury.
In this article, we'll list the do's and don'ts of hoisting a load with eye bolts and some common activities that make their use dangerous.
Use Eye Bolts for the Right Job
There are three basic types of eye bolts used in industrial applications, and all three come in two standard variations: plain and shoulder. These three types include:
Nut Eye Bolt
Nut eye bolts are threaded to structures such as wood or steel posts and are often supported by a hex nut. They're designed to have a rope or a cable fed through the ring, which allows hoisting. Their rings can be drop-forged, forming a single, uniform ring, or bent into a loop. The latter is only suitable for light-duty applications. Eye bolts with nuts are versatile, but one should pay attention to their working load limit.
Machinery Eye Bolts
Machine eye bolts aren't secured via a hex nut. Instead, their threaded shank length is designed to be installed into tapped holes prefabricated in various machinery and equipment. They're generally made for heavy-duty applications, and depending on their type, they can be used for both vertical and angular lifts.
Screw Eye Bolt
Screw eye bolts, also known as lag eye bolts and eye screws, feature screw threads instead of machine thread fasteners and are most commonly threaded into wood or lag anchors.
Plain Pattern Eye Bolts
Plain pattern eye bolts are made of simple threaded studs with metal rings on one end, allowing hoisting operations. However, they're only suitable for vertical lifts, as angular loads could bend or break them.
Shoulder Eye Bolts
This variation is usually featured in nut and machine eye bolts for use with angular loads. When a shoulder-pattern eye bolt is appropriately fitted and threaded, the shoulder should bear against the seat and reduce the bending stress on the shank, caused by angular loads.The rated working load capacity is significantly reduced when loading at any angle that isn't parallel to the bolt's shank.
Use Proper Eye Bolt Accessories for Lifting
Source: Reid Supply
Eye bolts must be properly "seated" against the elements they're used on. For example, suppose the shoulder of the machine eye bolt isn't seated firmly against the body of a 22kW electric motor (which weighs approximately 290lbs). In that case, it's susceptible to bending and breaking during angular loads. To ensure that the shoulder is firmly seated, hoisting and rigging accessories must be used — in this case, washers.
Bevel washers, for example, are used with eye bolts to correct the taper on I-beams and other structural applications. Rigging hooks are attached to chains, ropes, and slings used to lift and move large loads, while wire rope thimbles prevent other rigging fittings from damaging the cable. Always use the appropriate hoisting and rigging accessories to ensure safer lifting.
Do Not Overload Your Eye Bolts
Depending on their size and material, all eye bolts have their respective working load capacities or how much weight an eye bolt can withstand at a straight (no angle) pull. For example, stainless steel eye bolts with a 1/4 inch shank can usually hold up to 600lbs vertical lift. However, that load capacity drops to approximately 480lbs at a 15° angular lift, accounting for about a 20% loss in its maximum load capacity.
Vertical loads are always provided by the manufacturer or even marked on the eye bolt itself. On the other hand, angular loads have to be derived from the vertical load capacity and the angle of the pull. The pulling force must not exceed the rated load capacity, otherwise the eye bolt will fail, resulting in devastating and fatal consequences.
Do Align Your Sling Properly With Eye Bolts to Lift
To avoid damaging the eye bolts during hoists and lifts and thus incur their failure, it's important to use them safely. Always orient eye bolts in line with the slings; if the load is applied sideways, the eye bolt may bend or even break.
To guarantee that the eye bolt securely contacts the load surface, place washers between the shoulder and the load surface. Make sure the nut is torqued properly. When employing shims or washers, make sure that at least 90% of the threads in the receiving hole are engaged. Make sure that only one sling leg is attached to each eye bolt.
Do Inspect Your Eye Bolts Regularly
Just like any lifting equipment, eye bolts should be inspected for damage prior to each use, since any damage or wear increases the chance of failure. Eye bolts with nicks and gauges, bend, distortions, heavy wear, and corrosion should be removed from service and safely disposed of, preventing their accidental re-use.
This also applies if there are indications of heat damage, weld splatter or arc strikes, reparation marks, any kinds of alteration, or paint. Never paint, or use painted eye bolts, as coats of paint may help hide any evidence of damage during visual inspections. Instead, use stainless steel or hot-dip galvanized eye bolts if your application demands corrosion resistance.
Get Started Lifting With Eye Bolts Today
Eye bolts are the most commonly used hardware for hoisting and lifting applications, though they're also mostly misused due to improper and uneducated use. If you're in need of eye bolts, or any other type of hardware used in hoisting and lifting applications, you can find the necessary components at Reid Supply — one of North America's largest hardware suppliers, with over 40,000 different parts and components in stock. If by any chance we don't keep stock of a specific piece of hardware you need, contact us, and we'll source the parts and components for you.