At the heart of many heavy-duty applications like towing, hoisting, and lifting lies a seemingly unassuming component: the wire rope thimble. Yet, its role is nothing short of crucial.
Here, we’ll lay out everything you need to know about wire rope thimbles, including what they are and why choosing the right one for your loop application matters.
What Are Wire Rope Thimbles?
The job of wire rope thimbles is to protect wire rope loops. Wire rope thimbles play a significant role in maintaining the vitality of the wire ropes they support. Wire rope thimbles function as a shield for wire rope loops. When loops are subjected to force, the load becomes concentrated at the apex. The absence of a thimble accelerates stress. Thimbles act as a pad, offering much-needed structural support.
There are some key primary benefits that come with wire rope thimbles:
- Protection Against Fray: Thimbles don't merely prevent fraying; they become a barrier, a frontline defender against the wear and tear that ropes undergo. This kind of protection is particularly vital when ropes are subjected to rigorous or continuous movements, ensuring that the rope’s integrity remains uncompromised over time.
- Shield Against Kinks: Wire rope thimbles help maintain the rope's natural shape and alignment. Deformation leads to kinks. Kinks lead to breaks. With thimbles in place, wire rope loops continue to function optimally, safeguarded from failure.
My Wire Rope is Coated, Now What?
Do you want the loop to develop the wire rope's strength? If so, coating should be stripped at the loop and the thimble size should reflect the stripped wire rope diameter. For example, if 3/8" 7x19 GAC is PVC coated to 1/2"OD, then a 3/8" thimble would fit best with a stripped loop.
Are There Slings With Loops That Don’t Have Thimbles?
Yes, in fact, there are loop slings that omit thimbles. They are referred to as “standard loop slings” or “soft loop slings” in order to differentiate them from “thimble loop slings”. It’s important that these standard loops connect to round surfaces and not square edges. If the standard loop is sliding over a round pipe that would be appropriate. However, if the standard loop is connected directly to a flat bar or angle iron and then pulled taught, then the load would be potentially concentrated to a sharp edge or point. If the bearing point of a standard loop is forced into too tight of a bend radius, then it causes damage to the bearing points of the loop. It’s important to inspect standard loops frequently. If it’s kinked and/or bent out of shape, then it might be time to replace it. The inside length of a 6x19 class “standard loop” is typically sixteen times the wire rope diameter. For example, with 1/2" 6x19 class, the inside length is typically 8” (1/2"x16=8”). The inside width of the “standard loop” is typically half the inside length (8”÷2=4”). In other words, a 1/2" 6x19 class wire rope sling in new condition with a “standard loop” is typically 8” long by 4” wide, in a relaxed condition (under zero load).
Are There Slings With Both Standard Loop & Thimble Loop?
Yes, one variety of slings available has a standard loop opposite of the thimble loop. In some lifting applications, thimble reinforcement may only be advantageous at one side, depending on the connecting hardware.
When Don’t I Need a Wire Rope Thimble?
If the thimble would inhibit connection clearance, the exclusion may be appropriate. In some cases using one size up of a thimble may alleviate the clearance issue. In other cases, it might not. Sometimes wire rope loops might not be for lifting at all. Let’s say that the coated wire rope is for a security application. A thimble is atypical for security applications because the concern is tamper resistance (as opposed to a lifting application).
Diverse Shapes of Wire Rope Thimbles
The shape of a thimble significantly influences its fit, performance, and compatibility in varied applications. The main two shapes are teardrop and round.
- Teardrop: Resembling its namesake, the teardrop wire rope thimble is both elegant and functional. Its unique design often caters to specialized application needs, ensuring a precise fit for the wire rope it intends to protect.
- Round: The round wire rope thimble isn't just about its circular shape. Universally adaptable, it has versatility, making it a preferred choice for a broad range of applications.
Wire Rope Thimble Materials & Finishes
The essence of a thimble's effectiveness lies not only in its shape but also in the material it’s made of and the finish applied. These two factors play an instrumental role in determining the wire rope thimble's longevity, resistance, and suitability for varied environments.
- Zinc-Plated Steel: Beyond its lustrous finish, zinc-plated steel offers a formidable defense against corrosion. It ensures that the thimble remains resilient even in moisture-prone areas, prolonging its service life.
- Galvanized Steel: Not just known for its robustness, galvanized steel also boasts of its anti-rust properties. By providing a protective zinc layer, it stands as a shield against environmental adversities, particularly in industrial setups.
- Stainless Steel: A material synonymous with strength and elegance, stainless steel thimbles are celebrated for their resistance to both corrosion and high temperatures. Their pristine finish and durability make them a sought-after choice in marine applications and aesthetic installations.
Diverse Wire Rope Thimble Types: Function & Utility
Wire rope thimbles play pivotal roles in diverse applications, each design meticulously crafted to cater to specific requirements. Understanding these types and their inherent functions ensures optimal selection for targeted tasks.
- AN1111 Thimbles: Specifically designed for aircraft cables, these thimbles provide enhanced strength. Their robust nature ensures longevity even under extreme flight conditions.
- AN100 Thimbles: Often used in military applications, these thimbles emphasize both durability and precision. They cater to rigorous standards, ensuring consistent performance in high-pressure scenarios.
- FF-T-276 Type II Thimbles: Suited for standard-duty applications, these thimbles offer a balance between flexibility and strength. They're versatile, making them ideal for a wide range of general uses.
- FF-T-276 Type III Thimbles: Built for heavy-duty tasks, their construction is more robust, providing extra support. They're particularly sought after in industrial settings where maximum load-bearing is essential.
- Open Pattern Thimbles: As the name suggests, these thimbles offer an open design for easy installation. They're best suited for lighter loads, providing flexibility and ease of use.
- Slip Through Thimbles: Designed for quick, temporary installations, they enable ropes to slip through effortlessly. Their convenience makes them popular for tasks requiring frequent adjustments.
- Synthetic Rope Thimbles: Tailored for synthetic ropes, they offer the perfect blend of lightweight and durable design. Their compatibility with non-metallic ropes makes them ideal for marine and outdoor applications.
- Custom Thimbles: These are custom solutions crafted to meet unique specifications. They cater to specialized tasks where standard thimbles might not offer the desired performance.
Pro Tips When Specifying Wire Rope Thimbles
- Understand the Application: Before selecting a thimble, it's essential to understand its application. Knowing the kind of strains and stresses the wire rope will face can guide your choice.
- Material Matters: Each thimble material has its unique set of properties. Make sure to choose the one that aligns best with your application.
- Shape It Right: The shape of the thimble can influence its efficiency. Ensure the chosen shape is apt for your wire rope design.
Wrapping Up the Wire Rope Thimble Journey
Thimbles are more than simple fittings; they represent precision engineering and thoughtful design. Lexco® Cable stands at the forefront, ensuring every wire rope thimble, and wire rope product in general, reflects unparalleled expertise and quality. It's this dedication that makes Lexco® Cable the trusted name in wire rope assembly.
View Lexco®’s thimble catalog: Thimbles On Lexco Cable Manufacturers
Visit Gallery: Wire Rope & Accessories | Lexco Cable to see wire rope loop examples.
Watch this Lexco® video about wire rope thimbles https://youtu.be/m7PypbpgxsU?si=KLno1dVQPT_T41um.
Visit Lexco®’s wire rope term glossary to learn more about wire rope fittings and hardware Glossary & Literature Library - Resources - Lexco Cable
Contact the team at Lexco® Cable to find out more about how our team can grant you the confidence that your wire ropes are well suited to your application, and that your fittings and ends are durable and strong.