1. What are eye bolts?
Eye bolts are one of the most used in applications where the load is pulled away from the eye or toward the eye in material handling. They feature the simplest design but made from forged steel that has been quenched and tempered, commonly consisting of a threaded shank with a ring or eye at one end, can be threaded to structures such as wood, steel or concrete, and often lock by a nut. They are designed to create a lifting eye through rope, cable, or shackles that can be secured for their safe working load.
2. Type of eye bolts
Eye bolts are available in a range of sizes, materials and finishes, from small eye bolts to large eye bolt, but commonly there are five main types of eye bolts, include regular eye bolt, shoulder type eye bolt, lag eye screw, forged eye bolt, and stainless steel eye bolts.
Regular eye bolt is a non-shouldered eye bolt with a nut, it is designed to be inserted through a hole and secured on the backside with the provided nut. It can only be used for completely vertical straight line straight line pulls or supporting an overhead load only. It will bend and break if loaded at the side or angular loading, so it is not recommended for angular loading. For angular lifts, shoulder eye bolts are the better choice.
Shoulder eye bolt is also known as collared eye bolt, features a supporting shoulder or collar to provide more stability to the base of the eye, so that can be loaded with slings at angles or with any kind of angular loading, but the capacity will be lost at different angles loading, and make sure that the shoulder eye bolt is installed properly. If the shoulder is not completely flush, it can only be used for vertical lifts, equal to regular eye bolt. We can offer long shank collared eye bolt, and machinery eye bolt, called shoulder pattern machinery eye bolt, features a shoulder with shank, fully threaded shank but without a secured nut. It is designed to be screwed directly into threaded or tapped holes, used as a connection point in rigging applications.
- Lag eye screw is also known as lag screw eye bolt, which is a kind of eye bolts for wood, they are designed for screwing into the thimbles. So, they don’t have a working load limit assigned to them because they are not possible to determine the various densities and conditions of the wood the eye bolts are screwed into.
Forged eye bolts come complete with a drop-forged eye, and feature good hardness and strength can be used in heavy-duty lifting applications.
They are made from high tensile carbon steel, forged and annealed, making them higher thermal conductivity, lower melting point, more malleability and durability, and better heat distribution than stainless steel, perfect for heat treatment, ideal for cold weather applications, and maintain the structural integrity and performance even in cold environments.
Then they are anodized, hot-dip galvanised, or plated (gold, zinc, or tin) even phosphate coating finishes, which can effectively prevent corrosive substances from coming into contact with the carbon steel, and improve corrosion resistance.
Stainless Steel Eye Bolts
Stainless steel eye bolts have a high chromium content that forms an invisible layer on the steel to prevent corrosion, due to this reason stainless eye bolts will endure longer in decking, architectural and marine applications since their high polished finish compared with galvanized carbon steel eye bolts.
3. How are eye bolts measured?
The best way to understand eye bolt is from the eye bolt sizes, it should be taken from directly underneath the eye, for there are different types in the lengths of the shank. The image below shows markings and specifications that are common across all types of eye bolts.
- Shank diameter (thread) (A)
- length of the shank (B)
- Exterior eye diameter (C)
- Interior eye diameter (D)
- Overall length (E)
The diameter of the shank (A) and length of the shank (B) is the most important aspect for eye bolts because they will infect the working load limit and thickness of the material that the eye bolt will be installed into.
Please see the eye bolt size chart as per your need from our eye bolt and nut catalog.
4. How to calculate eye bolt capacity?
The eye bolts are available in various working load limit to lift different weights. So it is important not to exceed eye bolt capacity, which refers to the load a single eye bolt can lift when the load is applied through the shank of the eye bolt vertically.
As the sling angle occurs at any other angle, the eye bolt capacity begins to diminish. The greater the angle the more drastically the rated capacity is reduced. It is very important that riggers understand the angular loading of lifting eye bolt capacity chart to make their lift safely:
- 5 degrees 100% of working load limit
- 15 degrees 80% of working load limit
- 30 degrees 65% of working load limit
- 45 degrees 30% of working load limit
- 46+ degrees Not recommended
5. How to install eye bolts?
The correct installation of eye bolts is same important as choosing eye bolt, here are some tips for installation:
- Check the thickness of the material, then choose the right the eye bolt with enough length to go through.
- Tighten the nut make the eye bolt firmly seated and keep the eye bolt shoulder flush against the mating surface.
- Use steel washers to fill the space of the unthreaded part of the shank, but the thickness of the steel washer must not exceed one thread pitch.
We hope this article can help you with the selection and installation of eye bolts. If you’re interested in learning more about the eye bolts, please Contact Us today.
6. How to select the right eye bolt?
When selecting an eye bolt, it is important to know the correct eyebolt based on its type and capacity for the lift you are conducting.
- Plain or regular eye bolts (non-shoulder) are for vertical loading only. Not recommended for angular load applications.
- Use shoulder eye bolts for vertical or angle loading. Be aware that angular lifts reduce shoulder eye bolts capacities. Shoulder eyebolts should not be used for angular lifts greater than 45º.
- Never use the greater load than the load rated eye bolts capacity, if you are uncertain of the load, it is recommended to choose a larger size eye bolt to be on the safe side.
- Follow the manufacturer’s recommended method for angle loads.
Incorrect use of shoulder bolt
Shoulder eye bolt with load correctly applied
Incorrect way of applying angle load
7. What should you avoid when using eye bolts?
- Do not run a sling through a pair of eye bolts – it will reduce the effective angle of lift and will put more strain on the rigging.
- Do not force the slings through eye bolts. This force may alter the load and the angle of loading.
- Do not use eye bolts that have been ground, machined or stamped.
- Do not use bars, grips or wrenches to tighten eye bolts.
- Do not paint an eye bolt. The paint could cover up flaws.
- Do not force hooks or other fittings into the eye; they must fit freely.
- Do not shock load eye bolts.
- Do not use a single eye bolt to lift a load that is free to rotate.
- Do not use eye bolts that have worn threads or other flaws.
- Do not insert the point of a hook in an eye bolt. Use a shackle.
- Do not use a shackle that is capable of lifting more than the eye bolt – the eye bolt may become overloaded.
8. How should you use eye bolts safely?
- Orient the eye bolt in line with the slings. If the load is applied sideways, the eye bolt may bend.
- Pack washers between the shoulder and the load surface to ensure that the eye bolt firmly contacts the surface. Make sure that the nut is properly torqued.
- Engage at least 90% of threads in a receiving hole when using shims or washers.
- Attach only one sling leg to each eye bolt.
- Inspect and clean the eye bolt threads and the hole. Check for bends, cracks, or worn threads.
- Screw the eye bolt on all the way down and properly seat.
- Ensure the tapped hole for a screw eye bolt (body bolts) has a minimum depth of one-and-a-half times the bolt diameter.
- Install the shoulder at right angles to the axis of the hole. The shoulder should be in full contact with the surface of the object being lifted.
- Use a spreader bar with regular (non-shoulder) eye bolts to keep the lift angle at 90° to the horizontal.
- Use eye bolts at a horizontal angle greater than 45°. Sling strength at 45° is 71% of vertical sling capacity. Eye bolt strength at 45° horizontal angle drops down to 30% of vertical lifting capacity.
- Use a swivel hoist ring for angled lifts. The swivel hoist ring will adjust to any sling angle by rotating around the bolt and the hoisting eye pivots 180°.