Are leaf chain anchor pins a weak point in your lift system?
When it comes to forklift trucks and other materials handling equipment that use fixed leaf chains, the saying “A chain is only as strong as its weakest link” is not entirely true, as another weak point is potentially the anchor – where the leaf chain is attached to the lift system.
A key part of that anchor assembly is the leaf chain anchor pin – sometimes called a clevis pin. They often get overlooked, but they play a key part in safely joining the leaf chain to the leaf chain anchor bolts, therefore securing it into the lift system.
These pins are made from a specially produced alloy steel which is then heat-treated to increase surface hardness and abrasion resistance. At the same time, it is very important that the core of the leaf chain pin remains malleable as this ensures it will cope with repeated loads. The pin is also centrally polished to improve the roughness of the surface and to achieve a tight tolerance on the outer diameter.
The fit of the leaf chain anchor pin is very important – if it is too long, then it can snag or wear on other components in the lifting mechanism. If the pin allows for even a small amount of lateral movement it can change the loading on the leaf chain and chain anchor which could reduce the operating life of the leaf chain. When the pin is a little short it can be tempting to use a small split pin, but these do not cope well with side impacts.
Leaf chain pins are designed to connect the inner links of a leaf chain to the leaf chain anchor bolts. It should be almost impossible to push an anchor pin into the hole of the outer plate of a leaf chain, as the outer links are an interference fit or press fit – which means that the hole is slightly smaller than the pin diameter and the hole in the leaf chain inner links.
Some machine designs use a chain ending on the outer links of an anchor bolt. If you have this, then you should read: What are the pros and cons of fixing leaf chain using outer links?
The diameter of the chain anchor pin is determined by the leaf chain it is anchoring. The length is depending upon the design of the chain anchor – they can be manufactured to a wide variety of sizes and designs for the same type of leaf chain.
After the diameter, the next most important dimension is what we refer to as the “grip” which is the distance from inside to inside of the split pin holes. If for some reason, you do not have the pin, then let us know the diameter of the chain anchor bolt’s head – this will allow us to work out the “grip”.
We hold a number of different pin lengths for each leaf chain size to ensure that the pins fit the chain anchor correctly. For the most popular leaf chain BL634, we would regularly be using 12 different pin lengths plus the option of a connecting link. We also ensure the correct split pins are included.
When we receive an enquiry/ order we always double-check our extensive make and model database to ensure that the correct leaf chain with the correct anchor pin length is selected. By dealing with enquiries/ orders in this way we save valuable time and ensure we offer you the best technical solution.