Eye bolts, known for their convenient anchoring capabilities, are characterized by a looped head that distinguishes them from traditional bolts. Traditional bolts typically have a solid head with a recess or hexagonal shape, whereas eye bolts feature this unique looped head. Let’s examine the most common types of eye bolts in detail.
Forged Eye Bolts
Forged eye bolts are recognized by their forged construction, where raw metal is shaped under compressive forces like those from a power hammer. This process results in eye bolts that are generally stronger and more resistant to impact-related damage compared to other types.
Shoulder Eye Bolts
These eye bolts have a small lip or rim around their looped head, which aids in load distribution. The lip or rim acts similarly to a washer, distributing the load across the surface where the shoulder eye bolt is installed, ensuring more even stress distribution.
Screw Eye Bolts
Screw eye bolts are another type, featuring a pointed tip similar to a screw, but still retaining the looped head and threaded shank characteristic of eye bolts. The pointed tip differentiates them from other eye bolts that have a flat tip and allows for easier manual installation. Pressing the pointed tip against a surface allows the screw eye bolt to be twisted into place.
Bent Eye Bolts
Bent eye bolts are named for their bent head, unlike other eye bolts that have a complete, closed-off looped head. The head of bent eye bolts is bent during production to achieve the looped shape.
Swivel Eye Bolts
Swivel eye bolts are unique in their ability to rotate or swivel. They have a looped head connected to a threaded shank via a swivel mechanism. This feature is particularly useful in lifting and rigging applications, as it allows the load to spin without causing tangling of the chain or line attached to the swivel eye bolt.
In summary, each type of eye bolt serves a specific purpose, offering different advantages for various anchoring and lifting applications.
The Components of an Eye Bolt
Diverse Varieties and Structures of Eye Bolts: Understanding Their Components
Eye bolts, tailored for varied applications and specific uses, boast unique design elements. To better grasp the array of types and structures in lifting eye bolts, here are some key components:
- Eye – This is the loop at the top, a defining feature of the eye bolt. It can take various forms: bent, welded, or forged.
- Shoulder – Often referred to as the “skirt,” this part where the eye and shank converge is crafted to withstand bending forces.
- Shank – This is the threaded portion that connects to the eye, crucial for the bolt’s anchoring function.
It’s vital to choose an eye bolt that not only meets but potentially surpasses the working load limit for your specific task. Ensure it aligns with the Working Load Limit (WLL) of the slings and other rigging equipment in use.
Eye Bolt Markings and Identification
As per ASME B30.26 – Rigging Hardware standards, each eye bolt must be clearly marked to indicate:
- The manufacturer’s name or trademark
- The size or rated load capacity
- The grade, specifically for alloy eye bolts
- These markings are essential for ensuring the correct and safe use of eye bolts in various lifting and rigging applications.
Eye Bolt Materials
When selecting an eye bolt, the material is an important consideration, particularly if you require enhanced corrosion resistance for your application. The two most common materials for eye bolts are:
- Stainless Steel Eye Bolts
Stainless steel is highly valued for its ability to maintain corrosion resistance, even when it is scratched, dinged, or heavily used. This material is ideal for rigorous applications like rigging and tie-downs. Among the various grades, 304 stainless steel is the most common, while 316 grade is suitable for saltwater applications, offering resistance to ocean spray and salt.
- Galvanized Eye Bolts
Galvanized eye bolts are treated with a thin zinc coating, which protects the metal from corrosion and oxidation. These bolts are typically used in industrial applications where moisture is not a major concern but where there is still a need for protection against elements that could cause accelerated corrosion or deterioration.
Angular Loading of Eye Bolts and Rated Capacity
The working load limits for eye bolts are based on a straight vertical lift in a gradually increasing manner. Angular lifts significantly lower the working load limits and should be avoided whenever possible. If an angular lift is necessary, a properly seated shoulder pattern eye bolt must be used. Loads should always be applied to eye bolts in the plane of the eye, and angular lifts must never exceed a 45° pull.
Shoulder Eye Bolts: Working Load Limit Reduction with Vertical Angle
For shoulder eye bolts, it’s important to note that the working load limit decreases as the angle of the lift moves away from vertical. This reduction in load limit should be taken into account for safe and effective usage.