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image of screw pin shackle with screw untightened from the shackle body

Screw Pin vs. Bolt On Shackles: What's the Difference?

Shackles come in various makes and sizes for customized and optimal connection to equipment like lifting slingschain, and rope assemblies. But one distinguishing element - the type of shackle bolt - is crucial to choosing the right one that secures the best for your needs. We discuss the differences between screw-pin and bolt-on shackles, two prominent pin types, and determine which shackle bolt is right for you.

What Are Screw Pin Shackles?

Screw pin shackles are made with threaded pins that insert through one of the shackle's ears and screws into the other ear. This screw pin mechanism secures nicely and provides a strong, durable connection for your loads. When tightened properly, the threads of the screw pin become fully engaged, keeping hold onto the shackle's ear while the shoulder contacts the shackle's body. U.S. Cargo Control offers screw pin shackles in various sizes and makes, including galvanized and stainless steel versions.

Shackles with this particular pin type makes it easier for rigging tasks that require quick connection and release. Compared to other shackle types, screw pins offer the fastest connection and disconnection, making them the perfect choice for temporary jobs. 

What Are Bolt-On Shackles?

Bolt type shackles look similarly to screw pin shackles, except there are minor differences. The pin mechanism isn't threaded, and the combination of both a bolt and a cotter pin is used to secure the shackle instead of having to screw it into the other ear. The cotter pin on the end of the shackle bolt creates an additional security measure that gives them the alternative name "safety shackles."

Shackles with this bolt type work in similar applications as screw pin shackles, but they provide sustainable security over the long haul. The stronger security with bolt-on shackles makes them better for long-term applications or when loads are at risk of sliding on the shackle pin, which could cause other pin types to break or come loose.

image of screw pin shackle with screw untightened from shackle body

Which Bolt Shackle is Right For Me?

Both screw pin and bolt type shackles offer great benefits for your different lifting, rigging, and towing applications. When determining which shackle type is right for you, consider these factors:

1. Security

Security is vital when using shackles for any job. They need to stay in place and not break or come apart when in the middle of your task. With both of these pin types, you can rest easy knowing that these hold up well against most rigging applications.

However, the bolt type shackle provides more security than the screw pin. Additionally, the features of the bolt and cotter pin used to tighten this shackle makes it a superb choice.

2. Permanency

The other thing to consider is the length of your application - whether its temporary or permanent. Screw-pin shackles are not designed to be solutions for long-term applications. A big reason is due to readjustment, or re-tightening the screw to this shackle. As we said earlier, the threads on the pin are fully engaged when the shackle is in use. Over time, the pin slowly unscrews with each rigging job it handles.  

Bolt-on shackles, on the other hand, work in long-term applications and don't need readjustment after many uses. The unthreaded pin secures with just the cotter pin and bolt, which hold up longer than the threaded pin on screw pin shackles.

3. Style of Application

Next, determine which type of loads you work with and how you plan to use these products with them. Both of these shackles can be used for similar applications related to rigging, tie downs, towing, suspension, or lifting applications. However, some of these applications cater more towards one shackle versus the other. For example, screw pin shackles work for temporary applications like tie downs and and towing because of their quick release nature and threaded design. Bolt type shackles are better used for gathering multi-leg lifting slings and for suspending wire rope on steel structures.  

NOTE: You must always consider the working load limit (WLL) of your entire rigging task, including the shackles.

4. Possible Sliding & Rotation

Lastly, consider whether your load may experience any sliding or rotation during any rigging job. Screw pin shackles aren't the best to use when your load is at risk of rotating on the job. Examples of this include lifting slings, 

Bolt-on shackles handle rotation and warping much easier than screw pin ones. This is by design; the unthreaded pin secured by a bolt and cotter pin don't experience the same pull as threaded pins do.

different types of shackles hanging on a wire rope hanger

Other Types of Shackle Bolts

Besides the two types of bolt shackles listed above, we at US Cargo Control carry additional styles to accommodate different needs:

crosby round pin anchor shackle with red pin

Round Pin Shackles have a round, unthreaded pin that easily slides through the ears of the shackle and is secured in place using a cotter pin. These are great if your shackle will become subject to twisting and/or torque. Round pin shackles work primarily in applications with in-line loads, such as towing or tie-down. They should not be used for overhead lifting or as a collector ring in rigging applications. 

captive pin d shackle made of stainless steel

Captive Pin Shackles contain a screw pin that's "captured" on one of the shackle's ears, keeping it connected to the body at all times. This prevents the pin from disconnecting and falling off the shackle, losing the pin in the process. Captive shackles are mostly used for boating and other marine applications where the pin won't fall off into the water.



Shackles from US Cargo Control

While the pin type of your shackle can be critical to picking the right choice, there are other considerations to take into account.

U.S. Cargo Control offers different styles of shackles for you to choose from. Each style works best for different applications and pulls. Anchor shackles, or bow shackles, contain a rounder "O" shape that allows it to take the load in different directions. Chain shackles, or "D" shackles, are another variety with a much narrower body that can handle heavier in-line loads, and doesn't allow for loads to be taken in multiple directions.

We also carry different brands of shackles:

  • Crosby® offers the highest design factor in the industry (6:1) and are all load-rated and fatigue-rated for enhanced performance in various climates and working conditions.
  • Van Beest are European-made rigging products identified by their green shackle pins. Each of these high-quality shackles are made to meet all industry standards for lifting and rigging.
  • Chicago Hardware is a domestic manufacturer of shackles that distributes all kinds of shackle types including screw pin, bolt type, round, and more.

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