If you’ve ever lifted a heavy piece of construction equipment, a precast concrete panel, or a commercial HVAC unit, there’s a good chance you relied on a steel wire rope sling to do the job safely. As a supplier who’s worked with lifting teams, riggers, and project managers across the U.S. for over a decade, I’ve learned that most people focus first on a sling’s working load limit (WLL) or material grade—those numbers that tell you how much weight it can hold. But I’ve seen more than one lift go wrong because a team overlooked a far less talked-about but equally critical property: lateral rigidity. Steel Wire Rope Sling
Lateral rigidity isn’t a term that comes up in casual rigging conversations, and that’s part of the problem. Too many riggers treat all slings the same way, assuming strength is the only thing that matters. The truth is, lateral rigidity is what keeps a sling from bending, twisting, or swinging out of control mid-lift—especially when you’re working with large, unbalanced, or irregularly shaped loads. Let’s break this down, how it works, why it matters, and what it means when you’re choosing a sling for your next job.
First, let’s get clear on what lateral rigidity actually is, in the context of steel wire rope slings. Rigidity, in general, is a material’s resistance to deformation under force. Lateral specifically means “side-to-side,” so lateral rigidity is a sling’s ability to resist bending or shifting perpendicular to its length. Think of a rope: if you hold a length of thin twine and pull it tight, it’s easy to push the side of it and make it bend—low lateral rigidity. Now hold a length of thick, high-grade steel wire rope sling, pulled tight between two points. If you push the side of that, it takes far more force to bend it. That difference is all about lateral rigidity.
This property isn’t just one single number pulled from thin air—it’s a combination of several factors that go into making a steel wire rope sling. The first is the core construction of the rope itself. Most standard slings are made from 6×19 or 6×37 rope, but the number of strands and wires per strand makes a huge difference. 6×19 rope has thicker, fewer wires per strand, which means the individual strands are stiffer overall. 6×37 rope has thinner, more flexible wires, so it’s better for wrapping around small objects, but it has much lower lateral rigidity. That’s a trade-off every sling supplier has to navigate: flexibility for tight spaces vs. rigidity for stability.
Next is the lay of the rope—the way the strands are twisted around the core. Right-lay and left-lay are common, but the lay length (how much rope is in a full twist of strands) changes rigidity. A shorter lay means tighter twists, which make the rope stiffer in the lateral direction. A longer lay is more flexible, but it bends much easier side-to-side. The core of the rope also plays a role: fiber cores (FC) are lighter and more flexible, but they reduce lateral rigidity compared to steel cores (IWRC, or independent wire rope core). Steel cores add extra structure along the length of the rope, so when force is applied sideways, they don’t deform as much. For slings built for heavy, static lifts, IWRC is almost always the right choice for lateral rigidity, though it’s a bit heavier than FC.
Then there’s the way the sling is fabricated into its final shape. A sling that’s been looped and fitted with end fittings—whether those are thimbles, hooks, or master links—has different lateral rigidity than a raw rope, because the end fittings add structural strength at the points where stress is highest. The way the sling is spliced is also critical: a hand-spliced 7-part eye splice has more bulk and rigidity near the eye than a machine-spliced splice, which might be smoother but slightly less stiff. That bulk at the end fittings actually helps prevent the sling from bending where it connects to the lifting hardware, which is a common failure point.
Now, why does this matter in real-world lifting? I’ve seen two scenarios where lateral rigidity made all the difference between a safe lift and a dangerous accident. The first was a job in 2018 for a structural steel contractor in Chicago. They were lifting 12-foot-long steel I-beams for a new high-rise. The crew showed up with a set of 6×37 FC slings—light, flexible, perfect for wrapping around pipes, but not ideal for beams. As they lifted, the slings bent sideways under the weight of the unbalanced beam, causing it to twist mid-air. The beam swung into a nearby scaffolding, damaging a section and sending a rigger scrambling to avoid injury. We swapped their slings for 6×19 IWRC slings the same day, and the rest of the lifts went off without a hitch. The stiffer slings held their shape, kept the beam level, and eliminated the side-to-side bend that caused the swing.
The second example was a precast concrete plant in Ohio, where they’re lifting 8-foot-long concrete wall panels every day. Panels are flat, wide, and prone to shifting if the sling isn’t stable. The plant originally used generic slings that worked for their smaller loads, but once they upgraded to larger 10,000-pound panels, they started having issues with slings curling around the top edges of the panels, causing scratches and even partial slips. They switched to our custom fabricated slings with reinforced eyes and 6×19 IWRC construction, and the problem went away. The higher lateral rigidity meant the slings kept their flat shape when they were wrapped around the panels, so they didn’t curl inward. That not only prevented damage to the product but also made the lift safer, since there was less chance of the sling slipping.
A common misconception I run into is that thicker rope automatically means higher lateral rigidity. That’s partially true, but it’s not the whole story. A 1-inch-diameter 6×19 IWRC sling has more lateral rigidity than a 1.5-inch-diameter 6×37 FC sling, for example, because the construction is stiffer. The material grade also plays a part: high-strength carbon steel (like grade 80 or grade 100) is stiffer than mild steel, so a grade 100 sling will have higher lateral rigidity than a same-diameter grade 80 sling. It’s a balance between diameter, construction, core type, and material that we as suppliers have to calculate for each application.
So how do you measure lateral rigidity, for anyone who’s wondering? It’s not as simple as a WLL number stamped on the sling. Rigidity is usually tested in a lab, by applying a side force to a section of sling under tension and measuring how much it bends. The test is done at load levels close to the sling’s WLL, because rigidity changes as the sling is stretched under load—think of how a guitar string gets stiffer when you tune it, the same principle applies here. For a sling, the ideal level of lateral rigidity depends entirely on the load: a delicate, fragile object needs a flexible sling with lower rigidity to avoid damage, while a heavy, irregularly shaped load needs a stiffer sling with high rigidity to keep it stable.
This is why it’s so important to work with a supplier who understands the full picture of your lift, not just how much weight you need to lift. A lot of suppliers will just sell you the sling with the highest WLL, but that might not be the right one for your application. For example, if you’re lifting delicate machinery with sharp edges, a flexible sling with lower lateral rigidity might be better to avoid scratching the surface. But if you’re lifting large metal castings that don’t have even lifting points, a stiffer sling will keep the load from shifting side-to-side during the lift, which can prevent accidents and product damage.
I also want to clarify what lateral rigidity isn’t, because it’s often confused with other sling properties. It’s not abrasion resistance, though a stiffer sling might hold up better to rough surfaces if it’s built with a protective coating. It’s not fatigue resistance, though a sling that bends excessively will fatigue faster over repeated lifts. Lateral rigidity is a separate property that affects how the sling behaves during the lift itself, not how long it lasts or how well it resists wear.
As a supplier, this is something we emphasize in every conversation with a new customer. We don’t just ask “how much weight do you need to lift?” We ask what the load looks like: is it flat? Round? Unbalanced? Does it have sharp edges? What’s the lift height, and will the sling be wrapped around anything? All of those answers help us recommend a sling with the right level of lateral rigidity for the job. Last year, we worked with a wind turbine installation company that was lifting 75-foot-long turbine blades. They needed slings that were flexible enough to wrap around the tapered ends of the blades, but stiff enough to keep the blade from swinging during the 300-foot lift. We custom-built slings with a 6×25 construction (a middle ground between flexible and stiff) and reinforced end fittings that gave them exactly the right balance. That lift went perfectly, and they’ve been repeat customers ever since.
Another thing to consider is how lateral rigidity changes over the life of a sling. A new steel wire rope sling will have a certain level of rigidity, but as it’s used, it wears out. The strands can start to flatten, the wires can bend, and the core can compress, all of which reduce lateral rigidity. That’s why regular sling inspections are so important—not just to check for broken wires or corrosion, but also to notice if the sling has become too flexible. If a sling that used to hold its shape now bends easily side-to-side, it’s time to retire it, because it’s no longer safe for lifts that require rigidity.
I’ve seen too many riggers get hurt because they ignored a sling’s lateral rigidity, or because they didn’t even know it was a factor. A few years back, a small construction crew we’d worked with bought a set of cheap, generic slings from a big-box supplier for lifting heavy concrete beams. One of the beams was 20 feet long and weighed 8,000 pounds. As they lifted it, the sling bent so much sideways that the beam slipped, falling 10 feet to the ground and damaging it beyond repair. The crew was lucky no one was hurt, but they lost a $15,000 beam and had to delay their project for a week. When we looked at the slings, they were 6×37 FC, built for general lifting, not heavy, long loads. Their lateral rigidity was too low for the job, and that’s what caused the failure.
So what does this mean for you, when you’re choosing a steel wire rope sling? Don’t just look at WLL. Ask your supplier about the sling’s construction, core type, and how it will perform in side loads. Tell them everything you can about your load’s shape, weight, and how it will be lifted. If you’re lifting irregular, heavy, or unbalanced loads, prioritize higher lateral rigidity. If you’re lifting delicate, small, or wrapped loads, a slightly more flexible sling might be better to avoid damage.
At the end of the day, a steel wire rope sling is only as good as its ability to keep your load safe, and that depends on more than just how much weight it can hold. Lateral rigidity is the quiet workhorse of sling properties—something you don’t notice until it’s missing, and that’s when accidents happen. If you’re planning a lift and want to make sure you’re using the right sling for the job, whether it’s a custom solution for a unique load or a standard sling for your regular operations, we’re here to help. Our team has decades of experience matching slings to specific lift requirements, and we’ll walk you through every factor, including lateral rigidity, to make sure you get the right product for your needs.
Don’t take chances with your lifts. Reach out to us to discuss your next project, and we’ll help you choose a steel wire rope sling that’s safe, reliable, and built for your exact application.
Steel Wire Rope References
- ASME B30.9, 2022: Slings – Wire Rope. American Society of Mechanical Engineers.
- Rigging Handbook, 5th Edition. Occupational Safety and Health Administration (OSHA), 2020.
- Steel Wire Rope Sling Design and Performance Guidelines. Wire Rope Technical Board, 2019.
Nantong Shenwei Steel Wire Rope Co., Ltd.
Nantong Shenwei Steel Wire Rope Co., Ltd. is well-known as one of the leading steel wire rope sling manufacturers and suppliers in China since 1994. Our factory offers high quality steel wire rope sling made in China with competitive price. Welcome to contact us for quotation.
Address: No.1709, Zhangjiang Road, Nantong Economic Development Zone, Nantong City, Jiangsu, China
E-mail: nt@sw-steelwirerope.com
WebSite: https://www.shenwei-steelwirerope.com/
