- Published 9 Jan 2024
- Last Modified 6 Mar 2024
- 9 min
Shackles: The Complete Guide
This guide explains why shackles are used, how the various types of pins and bolts are used in industrial and domestic applications, and how they can affect their suitability for specific tasks or environments.
What are shackles?
Shackles, also known (albeit less commonly) by their older name, gyves, are primarily used as a means of lifting, securing or rigging heavy loads, objects and equipment. Lifting shackles are generally found as the final link in a connection chain or sling setup, where their key function is to make a robust physical connection between the load-lifting device (typically a hoist hook or sling) and the payload that needs to be moved or supported.
In a sense, they perform much the same role when used as lifting or rigging devices as all shackles do. Just like carabiners, handcuffs and various other types of shackling equipment, the point of a lifting shackle is to provide a strong and durable connection between two points, that can be opened and closed as required to either allow or prevent disconnection.
Although there are multiple different sorts of shackles available on the market, including snap shackles, twist shackles and headboard shackles, most lifting shackles can be designed and manufactured in one of two main configurations:
- D-type shackles, commonly referred to as chain shackles
- Anchor shackles, sometimes called bow shackles
Regardless of which type of shackle you’re using, it will generally consist of two main parts, namely the body and the pin (or bolt). The body of a shackle is broadly horseshoe-shaped or U-shaped, and the pin is affixed through both ends of the loop to create a closed link. Shackle pins or bolts are often threaded or part-threaded, but they can also take the form of clevis fasteners, with a cross-hole included for a split pin or tang to hold them in place once they’re secured through the ends of the shackle.
Different types of shackles and their uses
D-Shackles
D-shackles or chain shackles, also written as ‘Dee-shackles’, are, as the name implies, composed of a D-shaped body that’s narrower than the widely flared ‘O’ form seen in most anchor or bow shackles. Instead, D-shackles are shaped more like a standard chain loop or link.
They’re among the most common types of shackles found in a huge range of everyday scenarios, and the majority of other shackle types are essentially variations on the basic D-shape version. D-shackles are usually closed with a threaded pin or a clevis-type pin, and they’re generally seen as suitable choices for moderate to heavy loads that are being lifted in line.
For so-called side loads, in which the lifting being done is not necessarily completely vertical, D-shackles aren’t recommended as they can start to twist or bend if enough force is applied. In most side loading lifting applications, an anchor or bow-type shackle is the preferred configuration (see bow shackles, below).
Among the many different types of D-shackles available from suppliers and manufacturers today, some of the most common materials you’ll see listed in product catalogues include stainless steel D-shackles, zinc-plated or galvanised steel D-shackles, and various forms of alloy steel D-shackles.
Bow shackles
Bow shackles, also known as anchor shackles, are a more widely flared or O-shaped variant of the D-shackle format. One of the key advantages of bow shackles is that they’re much better equipped for handling multiple loads from different directions without it becoming a significant side load situation, as the rounded shape of the body makes them able to support heavier payloads at various points around their circumference.
Bow or anchor shackles can also accommodate far wider lifting straps than the narrower D-shackle variants (for all lifting and rigging jobs, the chosen shackle should be able to accommodate the strap or sling without requiring excessive pinching of the fabric). The trade-off for these advantages is a lower overall weight tolerance than an equivalent gauge D-shackle, provided the lifting is done strictly inline for the latter.
What are shackles used for?
Shackles have a great many uses in all sorts of settings, both industrial and domestic, although heavy-duty lifting shackles are of course more commonly found performing intensive workplace roles such as industrial crane rigging and on board large ships.
Lighter-duty equivalents are often seen being used on smaller items of equipment like luggage and tow ropes, or in personal safety gear including climbing and mountaineering harnesses.
Shackles offer a simple but effective solution in a wide range of heavy lifting, securing and rigging jobs, and are most often used in conjunction with other lifting equipment and accessories such as fabric or wire rope slings and webbing. In these sorts of roles, shackles offer a reliable, secure and strong point of attachment between the sling or other lifting device and the payload in question.
How to use shackles
While shackles themselves are quite straightforward pieces of equipment and relatively easy to use in most applications, the key to using them well is to know which kind of shackle is best suited to which kind of job.
Certain configurations of pins and shackle types are ideal for use in temporary tie-down or rigging arrangements, for example, while for permanent fixtures or much heavier lifting, other varieties of shackles and bolts must be used for improved safety.
For all shackle types, there are some widely accepted codes of best practice and safe use that should always be observed:
ALWAYS
perform a visual inspection of shackles prior to starting any lift (as required by law.)
ALWAYS
pay close attention to the manufacturer specifications for reduction in safe working capacities when operating under any degree of side load.
DON'T
perform the lift if any shackle fails to meet the required safety standards or appears to show signs of excessive wear
BE SURE
to connect multiple sling legs to the body of the shackle, and never to the pin itself.
ALWAYS
make sure you’re using the correct size of shackle for the hook or sling straps being attached.
NEVER
run a strap or sling body over a screw-type shackle pin, as it can move under load and eventually back the pin out of its threading.
Shackle sizes explained
You’ll frequently see a wide range of small, medium and large D-shackles or bow shackles listed for sale by size, and frequently the product information might include pin size as well. However, be aware that the key measurements given under any D-shackle specifications will be the diameter of the material used in the body section - the pin measurements will usually be longer than this.
It’s important to keep appropriate sizing (i.e. material thickness) in mind when planning and making a shackle purchase, as this is the key specification that will dictate the suitability of a given shackle for use under certain loads.
The first port of call for judging the suitability of a shackle for handling a certain payload should always be the manufacturer guidelines for safe working load (SWL). Sales should be backed up with clear information in this regard, and a product’s rated tolerance will often be visibly imprinted on the shackle itself.
Other measurement information - such as the pin length, or the distance between the shackle body eyes when new - is worth retaining access to throughout the working lifespan of the shackle, as it can help to diagnose and identify warping or bending over time. A shackle whose eye-to-eye distance exceeds that listed in the manufacturer’s specifications should not be used.
Pin types
Regardless of shackle body type, the load pin or bolt on a lifting shackle is fastened through the shackle body in one of various different ways.
One of the most common configurations is the threaded bolt or screw pin type - the threading on these pins may be complete on occasion, but more often it will only be partially threaded, to allow for a secure connection with the shackle body but without adding friction to the payload attachment elsewhere along the length of the pin.
Screw pin shackles are generally well suited to most temporary applications, provided there is no risk of the load moving significantly while supported. In some situations, this can potentially rotate the pin and gradually back it out of its threading. If a screw-type pin is deemed suitable for a particular task, one of its key advantages is that the entire shackle setup will consist of only two parts, and be notably quicker and easier to assemble/disassemble.
The other common type of shackle pin is the safety bolt version, in which a split pin holds a nut and bolt in place, acting as a clevis. The shackle then becomes effectively a three, four or even five-part component, which will be inherently less easy to set up and work with than a two-part screw pin shackle.
However, a safety bolt pin is far better suited to use in permanent connections, or in scenarios where there is liable to be some movement of the load that could cause a threaded pin to come unscrewed. Safety bolt pins are also a better choice when used in setups that don’t allow for particularly easy viewing/access to the pin for regular inspection purposes.
Safety, inspection and maintenance for shackle use
Because shackles are so often used for critical and intensive lifting and rigging applications, it’s extremely important to make sure you follow some basic safety checks and upkeep rules in order to guarantee more consistent levels of performance over time.
Shackles should be inspected regularly for any signs of general wear, tear and fatigue. Potential points of damage or failure for all shackle types can occur in the body, the pin, or in the eye or pin holes, and it’s important to monitor these areas especially closely over the working lifetime of all shackles.
In particular, inspect shackles carefully for any signs of bending, warping or stretching, which may indicate that the shackle is not coping sufficiently well with the load forces being placed on it. Bent shackles tend to be a sign of excessive side-loading forces, which can ultimately lead to catastrophic failure (particularly of D-shackles), while distorted or fractured pins should be replaced immediately.
Even if a pin remains entirely intact, it may not seat properly in the shackle if it’s even slightly warped from its original shape, which dramatically increases the risk of loosening under load. Shackle pins should never be forced or hammered into place if they’re reluctant to seat properly, and must never be replaced with a stand-in piece of hardware that wasn’t designed explicitly for that purpose and shackle type.