Jack chain is a type of chain made with a series of figure eight loops connected to each other at right angles. This type of chain comes in a wide variety of styles, for a broad assortment of purposes. As with any rope or chain product, it is important to make sure that the right chain is selected for a given application to ensure that it will be appropriate. If someone is not sure about what kind of chain is best, they should consult the staff of a hardware store.
Single jack chain, the basic style, has looped figure eights made from thin wire. Double jack chain is stronger, and designed for heavier loads and other applications. In either case, the chain can be made from brass, stainless steel, and other metals, and it can be treated to resist corrosion or may be left plain. Jack chain can also be stained, weathered, or otherwise treated for aesthetic purposes.
A common use for jack chain is in suspending signs, hanging flower pots, and similar objects. The chain is strong enough to support the weight, while providing give which allows it to shift in the wind. Jack chain also resists kinking, and should double back or knot on itself, which can be very useful in applications where it is subjected to agitation. For example, a sign suspended from two lengths of jack chain should hang straight and even because the chain will not twist or knot when the sign shifts with the wind.
Light fixtures can also be suspended with jack chain, and chain of this design can be used to tether animals as well. Many hardware stores carry several sizes and weights for people to choose from, with weight limits clearly indicated. It is important to buy chain which exceeds the anticipated load to ensure that the chain will hold up, and to buy treated chain if it is going to be used outdoors so that the chain will resist rust and other forms of corrosion.
In the timber industry, a jack chain is a looped chain with teeth which is used to move logs. The chain can rotate endlessly to move logs down the production line in a steady flow, ensuring that the sawmill can process raw timber in an efficient fashion. It is important to be careful around the jack chain because it poses a significant occupational hazard and can cause severe injuries or death in inattentive bystanders.