An eye bolt is a bolt with a loop at one end. They are used to firmly attach a securing eye to a structure, so that ropes or cables may then be tied to it.
Machinery eye bolts are fully threaded and may have a collar, making them suitable for use with angular loads up to 45°. Eye bolts without a shoulder should not be used for angular loads.
Heavy forged eye bolts with a continuous eye may be forged with an integral shoulder, allowing their use for heavy off-axis loads.
Eye bolts are often installed into masonry, and so versions that form their own anchor bolt are commonly available. Most of these screw into some form of shield anchor. Some lightweight forms are not screwed, but rely on just the pull on the ring itself to expand the anchor.
What are eyebolts?
An eyebolt is a mechanical fastener with a threaded shaft and a head forming a ring. Eyebolts are used to attach an eye to a structure, through which rope, cable or shackles can be secured. A common use is to create a lifting eye so that a crane can be attached to machinery, with special-purpose lifting eyes rated for their safe working load.
Low-strength eyebolts are often formed from a length of bar with the diameter of the nominal thread size. The head is simply bent into a ring from an unthreaded section of the bar.
These types of eyebolts can carry axial loads reasonably well but should not be used for off-axis loads. The opening where the end of the bar is closed to complete the ring may be welded but is likely to remain a possible point of failure.
High-strength eyebolts have forged heads that normally include a substantial shoulder. The shoulder enables them to support significant off-axis loads. The ability to support off-axis loads is often important in lifting applications where lifting slings with multiple legs are used to attach to multiple lifting eyes.
When lifting machinery, it is common for an eyebolt to be screwed directly into a tapped hole in the structure. In this case, an eyebolt is required that is fully threaded all the way up to the shoulder.
When an eyebolt is intended to be inserted through a hole and fastened by a nut on the other side, it is better if there is a shank. A shank is an unthreaded section of the shaft, below the shoulder, which provides a better transfer of load into the surface of the hole and is less likely to crack under fatigue loading.
How do Eye Bolts Work?
Eye bolts aren’t used for the same fastening applications as traditional bolts. Traditional bolts are typically used to secure two or more objects together. You can drive a traditional bolt through two objects so that the objects stay together.
Eye bolts still have a threaded body, so you can drive them into the same objects as their traditional counterparts. With that said, most eye bolts are used to secure ropes, cables, or chains.
You can secure a rope, cable, or chain to an eye bolt by connecting to the loop. The looped end of an eye bolt supports ropes, cables, and chains. This isn’t possible with a traditional bolt. Traditional bolts have a solid head, so there’s no way to connect a rope, cable, or chain to them.
Types of Eye Bolts
Different eye bolt designs are used depending on load direction, lifting angle, and application requirements.
- Plain Eye Bolts. Plain eye bolts are designed mainly for vertical lifting applications. They are commonly used where the load is lifted straight upward without angular force.
- Shoulder Eye Bolts. Shoulder eye bolts feature a shoulder between the eye and the threaded shank, allowing them to handle angular or side loads safely. These are preferred for more demanding lifting operations.
- Machinery Eye Bolts. Machinery eye bolts are forged and designed specifically for heavy-duty lifting of machinery, motors, and industrial equipment.
- Collared Eye Bolts. Collared eye bolts offer additional strength and are suitable for applications requiring improved load distribution.
- Anchor eyebolts: Eyebolts with some form of anchor bolt to enable fastening into masonry structures.
- Screw eyes (or eye screws): These are similar to an eyebolt but with a wood screw in place of a machine screw. These are used for attaching an eye to wood or plastic structures. Small screw eyes are used to hang picture frames and curtain wire.
- Ring bolt: An eyebolt with a captive ring passing through the eye of the head, effectively forming two chain links. This can reduce bending forces on an eyebolt.
- Eye nut: An eye nut is actually a nut which serves the same purpose as an eyebolt, although they are sometimes identified as eyebolts in catalogs.
- Pigtail eyebolts: These are formed from a length of bar, similar to ordinary low-strength eyebolts, but the head is bent into a helix so that it does not fully close on itself but can continue past 360 degrees. This allows the middle of a rope to be threaded into the eye without requiring access to an end.
- Roller eyebolt: These are designed to guide a rope or cable so that it can pass smoothly with minimal friction. The head is actually an assembly with four rollers retaining the rope that passes through it.
Applications of Eye Bolts
- Lifting and Material Handling. Eye bolts are widely used for lifting heavy machinery, equipment, and structural components in manufacturing plants, workshops, and construction sites. They provide secure attachment points for cranes, hoists, and pulleys.
- Construction and Infrastructure. In construction projects, eye bolts are used for lifting precast concrete elements, steel structures, and temporary supports. Their reliability makes them essential for safe site operations.
- Marine and Offshore Applications. Eye bolts are used in marine environments for mooring, rigging, and securing equipment. Stainless steel eye bolts are commonly preferred due to their corrosion resistance in saltwater conditions.
- Industrial Machinery and Equipment. Eye bolts are used to position, lift, and maintain heavy industrial machinery during installation or servicing. They simplify handling while reducing the risk of damage.
- Power Plants and Heavy Engineering. In power generation and heavy engineering industries, eye bolts are used for handling turbines, heat exchangers, and large components where safety and precision are critical.
Typical Materials of Eye Bolts
Most eye bolts are made from strong metals so they won’t break under heavy weight. The most common materials include:
| Material | Features | Common Uses |
| Steel | Strong, affordable, for heavy-duty jobs. | Construction, industry |
| Stainless Steel | Resists rust and corrosion, good for outdoor or wet places. | Boats, marine use |
| Brass | Good for light loads, resists rust, looks nice. | Decorative, indoors |
- Steel eye bolts often have zinc or galvanizing to stop rusting.
- Stainless steel works best if you need something tough in the rain or near saltwater.
- Brass eye bolts are more for looks or light-duty tasks.
That way you can pick the right type for strength, weather, or even style depending on what you need.
Eye Bolt Standards and Certifications
When you pick out an eye bolt, you need to know it meets the right standards. Standards help make sure each eye bolt is made for safety, strength, and quality.
Some common certifications and standards include:
- ASTM A193 Grade B7: Used for strong, threaded bolts, often needed for heavy lifting or tough situations. Eye bolts made to this standard are certified to perform in demanding environments.
- ASTM A193 Grade B8: Similar to B7, but for applications where corrosion resistance is important, like outdoors or around water.
It’s also a good idea to check if your eye bolt comes with a 3.1 certification. This certification shows that each bolt has been tested and meets quality requirements.
How to Properly Install an Eye Bolt
You’ll need the right tools and some basic steps to get a secure fit when installing an eye bolt. Making sure you understand the key safety rules is just as important as getting the bolt in place.
- Select the Right Eye Bolt. Choose an eye bolt that matches the required load capacity and is suitable for the intended use, whether it’s for angular loads (shoulder eye bolts), vertical loads (straight eye bolts), or dynamic applications (swivel eye bolts).
- Inspect the Mounting Surface. Ensure the surface is flat, clean, and strong enough to support the load without deforming.
- Drill and Tap (If Applicable). For wood or metal surfaces, drill a hole matching the bolt’s diameter and thread, then tap the hole to create internal threads for a secure fit. For concrete, use rated expansion or chemical anchors appropriate for eye bolts.
- Install the Eye Bolt. Hand-tighten the bolt until it’s fully seated. Use a wrench if necessary, but avoid overtightening to prevent thread damage. Ensure shoulder bolts sit flush with the mounting surface and position the eye to face the direction of the applied force.
- Test the Connection. Before applying full load, perform a load test if required by standards. Apply light tension to check alignment and stability, and inspect for rotation, movement, or any signs of loosening.
- Use Thread Locker (Optional). For added security, especially in high-stress environments, you can apply thread locker to the threads of the eye bolt to prevent loosening due to vibration or other factors.
Things to Consider When Choosing Eye Bolts
Eye bolts are available in different materials. Some of them are made of stainless steel, whereas others are made of carbon steel. Stainless steel eye bolts offer a superior level of protection against rust and corrosion. Carbon steel eye bolts, conversely, are stronger and more durable.
You should also consider the safe working load when choosing eye bolts. The safe working load refers to the maximum amount of weight that an eye bolt can safely support. Some eye bolts have a safe working load of 500 pounds. Other eye bolts have a safe working load of over 5,000 pounds.