How to Use an Eye Bolt

eye bolt galvanized machine rigging application

An eye bolt is a very common and fundamental piece of rigging hardware used to create secure anchor points in various lifting and rigging applications. Their signature design provides easy accessibility for rope and rigging hooks to either loop through or attach to without compromising under serious tension forces. Knowing how to secure these devices, however, is imperative to ensure it functions properly and safely while reducing the risk of breaking, bending, or damaging its surroundings.

Read on to know more about eye bolts and their different types, as well as how to use them effectively in the safest ways possible.

What is an Eye Bolt?

stainless steel eye bolt

An eye bolt is a versatile fastener that consists of a looped or circular-shaped head, known as an eye, and typically threaded on the other end, or the shank, for easy and secure fastening. The eye allows for hooks to attach to, as well as wire rope and cable to be threaded through, as a secure rigging point. This device works in a wide range of different lifting, anchoring, hoisting, rigging, and pulling applications.

Eye bolts provide a solid anchor point that fastens to objects with their threaded ends. The simple design of this device makes it incredibly versatile and an indispensable tool for establishing secure connections. 

Types of Eye Bolts

There are many different types designed for specific applications and uses. We offer these devices from various materials, fabrications, fastening types, and shoulder designs so you can find the right ones for your needs. Choosing the wrong type of eye bolt can be detrimental to your application, putting your load, equipment, as well as personnel at risk of getting injured.

Galvanized vs. Stainless Steel

Eye bolts come in two main types of materials: galvanized and stainless steel. Both are strong, durable metals made to withstand rust, corrosion, and some of the harshest elements while maintaining their strength and quality. To decide on the best option, you need to determine how important corrosion resistance is to your application.

Stainless steel contains high anti-corrosion properties from its alloy composition of chromium and low carbon steel that hold up even when it becomes scratched, dinged, or beat up. These devices are available in two types of metals:

    • Type 304: This is a common type used in automotive, construction, and agricultural applications. Its resistance to typical rusting and oxidizing acids keeps it strong in crucial setups.

    • Type 316: This "marine grade" variety contains molybdenum, an element that holds up against salt water, making these eye bolts perfect for marine applications and in environments with high moisture and high chloride levels.

Galvanized steel, on the other hand, is generally a cheaper option to use with similar protection. Its thin coating of zinc oxide protects it from harsh elements while maintaining its strength.

Forged vs. Non-Forged

You can also choose your products based on their eye formation. Forged eye bolts are made by pressing or hammering the top part of the device, changing the composition of the eye into an endless loop. This makes the device much more durable and performs well when lifting and rigging heavy-duty loads.

Non-forged, otherwise known as turned eye, wire eye, or bent eye, are made by bending the top unthreaded part of the bolt into the signature eye shape without creating an endless loop. These types come as welded or non-welded eye bolts. They work mostly for lighter-duty applications and not in any situation with the possibility of heavy loads or angular pulling.

Fastener Types

There are different ways in which you can fasten an eye bolt based on how it was made. These depend on how you plan to use it:

    • Nut & Washer: Standard eye bolts contain a nut and washer that fastens to the threaded rod of the device. 

    • Machine Bolt: Machine bolts look like shorter, stubbier standard versions. These devices do not insert through their objects. Instead, they fasten using pre-drilled holes created specifically as lifting points.

    • Screw Eye Bolt: Also known as lag eye bolts, this type of device contains an eye with a screw attached to it. Unlike the other types with a solid thread, the threads of this device taper off to a point that screws into wood and other anchor points for light-duty applications.

Shoulder vs. Non-Shoulder

Lastly, you need to choose your eye bolt based on shoulder type. The shoulder of the device is where the eye and the shank converge. This super critical area endures a lot of the pulling forces in lifting and rigging applications, especially with angular loading.

Shoulder eye bolts provide much more versatility by reducing the tension forces on the shank and allowing for angular loading, as well as straight line pulling. The shoulder eye bolt must be flush with the object for safe usage. Non-shoulder versions do not contain this feature and should never be used for angular loading.

eye bolt used for lifting bar

How to Install an Eye Bolt

  1. Determine the Thickness of Your Attachment Object
    Before installing, make sure you measure the thickness of your object you want to fasten your eye bolt to. This ensures you choose the right length for your application. Standard threaded versions should have their threads showing from the back side of the object. For machine and screw eye bolts, measure the thickness so that your device won't go through the object. 

  2. Insert the Eye Bolt
    After establishing the thickness, then you want to identify or tap holes into the object where you want to secure your devices. These holes need to be aligned with the diameter of the threaded rod to keep it seated against the object, preventing any wiggle room.

    Machine eye bolts require pre-drilled holes into the object. For drilling and tapping, the length of the hole's depth should equal the length of the device plus one-half the diameter of the rod. 

  3. Fasten the Eye Bolt
    For standard eye bolts, fasten them with the included nut for proper securement. If the unthreaded portion of the device sticks out below the anchor object, then add additional washers to keep the unthreaded part unexposed. This keeps it firmly fastened to its object without shaking loose from the protruding unthreaded portion.

rated capacity loads for angular pulling eye bolts
Image from E-Rigging.

Angular Loading and Rated Capacities

Often enough, loads are pulled in different angular directions. This occurs a lot in different rigging setups and with multi-leg lifting slings. Shoulder eye bolts are the only version that allows angular lifting and rigging to be done. The added shoulder component, when flush with the object, provides protection for the threaded rod and prevents it from breaking off.

When loads are pulled at a straight line perpendicular to the object, the rated load capacity is at 100%. However, the more you increase the angular pull, the lesser the rated load capacity becomes. The image above shows the substantial decreases as the angular pulls increase.

Safe Rigging with Eye Bolts

Just like with any other rigging hardware device, safety needs to be at the forefront with each and every use. Here are a few tips to follow when using these devices:

  • Always inspect your eye bolts for residue and damage before each use.
  • Never use standard non-shoulder eye bolts for angular pulling; always use in straight line pulls.
  • Never pull 
  • Always use these devices within their rated working load limits (WLLs).
  • Ensure your anchor points are secure for your application.
  • Keep eye bolts tight through the object and flush with the object for proper usage.
  • For lifting applications, orient the eye bolts in line with the slings. Use additional washers to alter the direction while keeping the bolt secure.

If you need help with choosing the right eye bolt for your needs, then give our team of product experts a call today for help!

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