316 Stainless Steel Anchor and Chain Shackle Guide
TEMCo's 316 stainless steel anchor and chain shackles are designed to withstand the harshest of environments. Stainless steel is an alloy that contains the chemical element chromium, which provides resistance to rust, corrosion, and staining. 316 grade stainless steel adds the alloy molybdenum, which provides the ultimate resistance to the effects of persistent salt water exposure. Though products made with hot-dipped galvanized steel provide great strength and excellent resistance to rust and corrosion, when exposed to salt water, they will eventually develop pockets and weaknesses as the zinc coating begins to corrode.
If, however, your application does not require the extra corrosion and rust resistance against salt water 316 stainless steel provides, please check out our galvanized steel lifting products here.
Choosing the Right Shackle
There are pros and cons to each shackle based on the application you plan on using it for.
If the application you are using the shackle for requires a line to remain in an unwavering straight line, the design of the chain shackle is ideal. As the line becomes taut, the shackle is designed to orient itself in the proper direction of chain pull, as seen above.
If the application requires multiple directions of pull or even multiple load bearing lines, an anchor shackle is perfect for the task. The design of the anchor shackle is suitable for situations where the load constantly change directions, which makes the anchor shackle the most popular choice for use on sailboat anchor lines.
The downsides to each depend on how varied your direction of chain pull might be. If your task requires you to keep a load line straight then an anchor shackle will work well, but may require adjustment to ensure the shackle has not moved off center. If your task has slightly angled directions of pull, a chain shackle will work, but may push the limits of a safe working load.
It is important, therefore, to also mind the safety protocols of your application in regards to using shackles as well as other rigging accessories. The following section will briefly cover some of these safety details.
Safe Working Load and Minimum Breaking Load
The minimum breaking load of a shackle is the amount of force required for the shackle to catastrophically fail. In other words, it is the least amount of force required to break the shackle. The minimum breaking load is not a safe working load. The safe working load, also called the working load limit, is calculated as a percentage of the minimum breaking load.
Though we do provide factory-tested minimum breaking load specifications for each of our shackles, we do not provide a safe working load specification since such a specification is relative to the application. We recommend you consult other sources to determine the safe working limit particular to your application, as well as other safety concerns not covered in this brief guide.
Anchor Shackle Directions of Chain Pull
The unique design of the anchor shackle allows the user to achieve directional load at angles, as well as the ability to attach multiple lines of load. (Though our chain shackles can take some directional load, it is not their intended design.)
Safe Working Loads for Directions of Chain Pull
Once you have determined your safe working load, a single load line can be taken at an angle from the center of the shackle. At a 45° angle, your safe working load limit is now at 70% of the safe working limit when the load lines are completely straight. At a 90° angle, your safe working load limit is now at 50% of the safe working limit when the load lines are straight. In short, as the angle of the direction of chain pull increases, your safe working load decreases.
Safe Working Loads for Multiple Load Lines
You can also have two or more load lines on a single shackle. When multiple lines are attached, do not exceed an angle greater than 120° between the outermost two lines. Calculating the safe working limit depends on the angle in which your lines are from the center of the shackle.
Avoid Direct Side Load
Finally, though the anchor shackle is designed to take directional load, it is not designed to take direct side load. When used in rigging or any application, ensure that the shackle is oriented in the above diagramed positions. Failing to follow these design parameters may result in injury and damage to your property.
Safety Wire and Mousing
Adding safety wire, or "mousing" your shackle, is a necessary task to ensure the clevis pin does not unscrew from the shackle, which results in potential personal injury or loss or damage to your property.
For maritime and any other application where strength and corrosion resistance are necessary, we highly recommend using TEMCo 316L Stainless Steel 20 AWG (0.032" diameter) Wire. Note that metals can react to stainless steel. Choosing the wrong material for your safety wire may result in bimetallic corrosion, a process in which either the wire or the shackle itself may suffer severe and rapid corrosion.
To mouse the pin to the shackle, cut a long piece of wire from your spool. Pass the wire through the hole in the clevis pin and form a figure eight around the side of the shackle, loop down, and pass through the clevis pin hole. Pull the wire down tightly to ensure the figure eight is secure. Do this for at least three passes, then clip and discard the excess wire. See the above photograph for a properly moused shackle.
For a temporary and quick moused shackle, using a zip tie will work. We do not recommend this option for maritime use.
Finally, leverage can be applied to the clevis pin with the bored center hole via a screwdriver or rod for a secure lock. It can also be used to leverage open a seized pin. Note that if a pin is seized, using your favorite lubricant is necessary to prevent galling of the threads.