What is an eye bolt?
An eye bolt is a bolt with a looped head with screw threads at the other end. They are often made in one piece, either bent or forged into shape, but for high loads those with welded loops are used as they can withstand loads up to the tensile strength of the metal from which they are made, thus ensuring there is no danger of the loop being forced open by the weight of the load.
Although eye bolts are sometimes made from wood, more commonly they are manufactured in metal. Industrial eye bolts are usually made from steel.
Welded eye bolts have a fully closed circular loop welded to the bolt, these tend to be used in installations requiring excessive strength, forged eye bolts have a loop that is partially open.
Eye bolts can be plain or made with a shoulder, i.e. a collar between the loop and the thread, these can be used in installations where the tension is not from a vertical or horizontal load but is coming from an angle.
The type of eye bolt used therefore will depend not only on the strength required but also the desired durability, i.e. how permanent the installation is to be, and the direction of the load.
Where eye bolts are used
Eye bolts have many uses, depending on their size and strength, from the smallest, such as those used to attach string to the back of a painting to allow the painting to be hung from a nail in the wall, to much larger ones that are used for industrial applications such as tie-downs, lifting and attaching steel wires to fence posts.
Typical industry sectors
Eye bolts are widely used in numerous installations, for example:
- Industrial lifting and material handling equipment
- Industrial rigging where steel eye bolts are ideal as anchor points
- Marine rigging where the eye bolts used are usually stainless steel
- Industrial installations such as stainless-steel balustrades
- Leisure industry where they are used in, for example, zip wire installations, also for securing shade sails
- Dockside cranes where heavy duty swivel eye bolts that will automatically adjust to the direction of the load are used
Stainless steel eye bolts are used wherever there is a danger of failure of the equipment due to corrosion, such as frequent contact with chemicals or water.
Sizing and typical range of sizes
Eye bolts are sized primarily by the length of the screw thread, some have full threads i.e. threads that go right to the loop, some have threads finishing before the loop. They are available in variety of shapes and sizes to accommodate all specific needs; the loop shapes vary between circular and oval.
Eye nuts are sometimes used in place of eye bolts. They perform the same function as eye bolts but they consist only of the loop. In place of the threaded part of the bolt, the nuts have a threaded hole in the loop through which the rope/cable is inserted and then tightened.
Other names for eye bolts
Wire eye lags which have a wood screw thread for use in wood, they in turn are known by other names: eye screws or turned/bent eye lags.
Long Shank screw eyes – as the name suggests these have long shanks and are also known as Vine Eyes as they are most useful in training vines or other similar plants.
Eye Bolts and Eye Nuts are commonly known Lifting Bolts and Lifting Eyes respectively, both are commonly known as Lifting Eyes.