Wire Rope Slings & Rigging Guide

Wire rope construction

Wire rope is constructed from individual steel wires twisted into strands, and strands twisted around a central core. The construction designation — for example 6×19 or 6×36 — describes the number of strands and the number of wires per strand. Understanding these designations is the foundation of correct wire rope selection.

6×19 classification

A 6×19 rope has 6 strands, each containing 16 to 26 wires. The relatively fewer, larger wires per strand make this rope stiffer and more resistant to surface abrasion — the thick outer wires resist wear from contact with sheaves, drums, and abrasive loads. The trade-off is reduced flexibility and lower fatigue resistance from repeated bending. 6×19 is the standard choice for lifting slings, boom pendants, and static or semi-static applications where abrasion resistance matters more than flexibility.

6×36 classification

A 6×36 rope has 6 strands, each containing 27 to 49 wires. More, finer wires per strand produce a significantly more flexible rope with higher fatigue resistance from repeated bending cycles. The finer wires are more susceptible to surface abrasion than 6×19. 6×36 is the preferred choice for crane hoist ropes, running ropes on winches and machinery, and any application involving continuous bending over sheaves or drums.

7×7 and 7×19 — aircraft cable construction

These smaller-diameter constructions (7 strands of 7 or 19 wires) are sometimes called "aircraft cable" in trade catalogues. They offer high flexibility in small diameters but are not rated for overhead lifting applications. They are appropriate for marine rigging, guy wires, safety lines, and similar light-duty control and tension applications. Do not use 7×7 or 7×19 construction for vertical lifting of personnel or equipment in industrial applications.

Core type: IWRC vs fibre core

The core runs through the centre of the rope and supports the strands. Two core types are standard:

• IWRC (Independent Wire Rope Core): A wire rope core — essentially a smaller wire rope at the centre. IWRC provides superior crush resistance, maintains rope geometry under side loads, and increases the rope's overall breaking strength by approximately 7.5% compared to the equivalent fibre core rope. IWRC is the correct choice for cranes, hoists, and any application where the rope passes over sheaves or is wound on a drum under tension.
• Fibre core (FC): A core of synthetic or natural fibre. More flexible than IWRC, provides cushioning between strands, and is preferred in applications where flexibility is prioritised over crush resistance. Less suitable for heavy drum-winding or applications involving significant side loading. Common in sling construction and lighter-duty lifting applications.

Grade and finish

Wire rope is available in several strength grades: IPS (Improved Plow Steel), EIPS (Extra Improved Plow Steel), and EEIPS (Extra Extra Improved Plow Steel) — each progressively stronger. For general industrial and lifting use, EIPS is the standard grade. Finish options include bright (uncoated), galvanised, and stainless steel. Galvanised wire rope offers corrosion protection for outdoor and marine environments. Stainless steel (typically 316 grade) is used where maximum corrosion resistance is required — marine, food processing, chemical environments — but carries a significant cost premium and has lower strength than equivalent carbon steel rope.

WLL, SWL, and Rated Capacity — Australian terminology

The terminology used in Australian rigging and lifting has changed, and using the wrong terms creates both compliance and safety risks.

WLL (Working Load Limit) is the current standard term for the maximum load a piece of rigging equipment — sling, shackle, hook, hoist — is rated to carry under normal conditions. WLL is calculated by dividing the minimum breaking load (MBL) by a design factor (safety factor). For wire rope slings the design factor is 5:1; for chain slings it is 4:1; for synthetic slings it is 5:1. A sling with a 50 kN MBL and a 5:1 design factor has a WLL of 10 kN (approximately 1 tonne).

SWL (Safe Working Load) is the old term, replaced by WLL. Australian Standard AS1418.1-2002 removed SWL from the standard for cranes, hoists, and winches. In the current framework, WLL is used for items below the hook (slings, shackles, hooks) and Rated Capacity is used for the crane or hoist itself. You will still encounter SWL on older equipment and in older documentation — treat it as equivalent to WLL for practical purposes, but specify WLL in new work.

For a complete breakdown of Australian rigging terminology — including why SWL was retired, how to calculate WLL from MBL, sling angle derating tables, and the weakest link rule — see our SWL vs WLL vs MBL Guide.

Sling types: wire rope, chain, and synthetic

Three sling types dominate industrial lifting: wire rope, alloy chain, and synthetic (web or round). Each has specific strengths, limitations, and correct applications. Selecting the wrong type for the environment or the load is a common source of premature failure and unsafe lifts.

For Grade 80 and Grade 100 chain sling configurations, WLL tables, and sling angle de-rating calculations, see the Chain Sling Guide.

Hitch types and WLL factors

Every lift uses one of three fundamental hitches — or a combination of them. The hitch configuration directly affects the effective WLL of the sling, and this is not a minor adjustment. Getting the hitch type wrong can mean working at twice the intended WLL without realising it — or losing half the sling's capacity through incorrect wrapping.

Vertical hitch (straight hitch)

The sling runs vertically from the hook to the load, with one eye on the hook and the other attached directly to the load. The sling's full rated WLL applies. This is the baseline: all WLL ratings on sling tags are referenced to vertical hitch. Use for loads with a reliable lifting point directly above the centre of gravity, such as an engineered lifting lug or a certified lifting point on machinery.

Choker hitch

The sling wraps around the load and the eye is passed through the opposite eye (or a dedicated choker fitting), forming a self-tightening loop that grips the load as tension builds. Effective WLL is 75–80% of the vertical WLL when the choke angle is 120° or greater. At tighter choke angles, the WLL reduces further. The choker hitch is useful for irregularly shaped loads with no lifting lug, but it must not be used on loads that would be damaged by constriction, and the rope must seat fully into the choke before the lift begins.

Basket hitch

The sling cradles the load beneath it — both eyes to the hook, load supported in the bight of the rope. When the legs hang vertically (90° to horizontal), each leg carries half the load, effectively giving up to 200% of the vertical WLL. This is the only hitch that multiplies capacity. The multiplication factor reduces as the basket angle narrows — see the sling angle section below. The load must be balanced; an unbalanced load in a basket hitch will slide to the low side and potentially roll off the sling.

Sling angle: the most misunderstood factor in rigging

Sling angle — the angle between the sling leg and the horizontal — is the single most commonly underestimated factor in rigging calculations. Most people intuitively feel that two sling legs sharing a load must be safer than one. They are, but only when the angle is favourable. As the angle decreases (the legs spread wider, or in a basket hitch, the horizontal distance between hook and load attachment increases), the tension in each leg rises sharply — far beyond what simple geometry suggests.

At 90° (sling legs perfectly vertical), the tension in each leg equals half the load weight — this is the ideal case. At 30° from horizontal (a very wide spread or a long, flat basket hitch), the tension in each leg equals the full load weight. Adding a second leg has provided zero additional capacity. Below 30°, the tension exceeds the load weight in each leg — the two-leg arrangement is actually more dangerous than a single vertical sling of the same rating.

The angle factor (reduction multiplier applied to the sling WLL) at common angles:

Most rigging standards — including Australian practice guidance — set 30° as the minimum permissible sling angle. Rigging below 30° is prohibited on most Australian worksites. If the geometry of the lift forces a low sling angle, the correct response is to use longer slings (raising the hook point relative to the attachment points increases the angle), not to accept the reduced capacity.

In practice: before any multi-leg lift, sketch the geometry and calculate or estimate the sling angle. If in doubt, measure the height from attachment point to hook and the horizontal distance between attachment points, then calculate: sling angle = arctan(height ÷ half-horizontal-distance). If this gives an angle below 60°, reconsider the rigging arrangement.

Shackles: D shackle vs bow shackle, screw pin vs safety bolt

Shackles connect slings to loads, slings to hooks, and hardware to hardware. They are the most commonly purchased rigging item — d shackle and bow shackle together represent some of the highest search volumes in the rigging category for a reason. For a full guide to shackle grades, WLL tables and AS 3776, see our Bow Shackle & D-Shackle Guide. Getting the shackle wrong does not always produce an immediate failure — it can produce a slow-developing failure as the pin loosens under load rotation, or a sudden failure when a D shackle is side-loaded beyond its rated direction.

D shackle (chain shackle)

The D shackle has a narrow, D-shaped bow designed to carry load in one direction: along the axis of the shackle body, through the pin. It is strongest in this straight-line configuration. Side loading — force applied across the width of the bow — drastically reduces the shackle's capacity and can cause the bow to open or distort without the pin failing first.

D shackles are the correct choice for single-point connections where the load direction is predictable and stable: connecting a sling eye to a chain link, attaching a single-leg sling to a machined lifting lug, or creating a point-to-point connection in a rigging assembly. They are not suitable for connecting multiple sling legs or for applications where the load direction may rotate or shift.

Bow shackle (anchor shackle)

The bow shackle has a wider, rounded bow that can accommodate multiple sling eyes or accept load from multiple directions without the severe derating that affects a D shackle under side load. This makes the bow shackle the correct choice for multi-leg sling assemblies, angled loads, and any application where load direction may shift during the lift.

Bow shackles have a lower WLL than D shackles of the same pin diameter because the wider bow creates higher bending stress in the body. They also take up more space — relevant when working in tight rigging assemblies. For most crane lifting and rigging work on construction and industrial sites in Australia, the bow shackle is the standard general-purpose choice.

Screw pin vs safety bolt (bolt-type) shackle

Both bow and D shackles are available with two pin types, and the choice matters as much as the shackle type.

Screw pin shackles have a threaded pin that is wound in by hand. They are fast to connect and disconnect, making them convenient for frequent pick-and-place operations where the rigging configuration changes between lifts. However, a screw pin can rotate and unwind under vibration or load rotation — particularly when used in a choker hitch where the sling naturally rotates as it tightens. If a screw pin shackle is used in any application involving vibration, rotation, or sustained load, the pin must be moused (secured) with wire through the pin hole to prevent it backing out.

Safety bolt (bolt-type) shackles have a smooth, unthreaded bolt pin locked by a nut and cotter pin (split pin). They cannot unwind under vibration or load rotation. They take longer to fit and remove, making them less convenient for frequent re-rigging but correct for permanent or semi-permanent installations, vibrating machinery, rotating loads, and any overhead lift where a dropped pin is a hazard. Safety bolt shackles are the required type for most permanent lifting point installations on Australian industrial sites.

Key rules for shackle use:

• Never side-load a D shackle — use a bow shackle if the load direction is not strictly axial.
• Never cross-load a shackle pin — the load must bear on the bow, not the pin.
• Never use a shackle as a hook by passing the pin through a load rather than the bow through the attachment point.
• Mouse screw pin shackles in any application with vibration, rotation, or sustained load.
• Rated shackles in Australia should comply with AS2741-2002. Check for a WLL stamp on the bow.

Wire rope fittings and terminations

Wire rope slings and assemblies require end terminations — the fittings that connect the rope end to the load, the hook, or the next piece of hardware. Termination type significantly affects the efficiency of the connection: how much of the rope's breaking strength is retained at the termination.

Termination efficiency

Thimbles

A thimble is a grooved metal insert that fits inside the eye of a wire rope sling at the termination point. Its purpose is to protect the wire rope from the sharp-radius bending it would experience if the eye were draped directly over a hook or shackle pin. Without a thimble, the wires at the eye contact point are bent sharply, reducing the effective strength of the termination and accelerating fatigue at that point. All rigging-grade wire rope slings should be thimbled. The d/d ratio (ratio of the thimble pin/contact diameter to the rope diameter) should be a minimum of 6:1 for the thimble to preserve the full rated efficiency of the termination.

Wire rope clips — never saddle a dead horse

Wire rope clips (also called Crosby clips, bulldog grips, or U-bolt rope clamps — distinct from the U-bolt fastener family covered in our U-Bolt Guide) are the most field-accessible way to form an eye in a wire rope. They are also the most commonly misused rigging component on Australian worksites. The consequences of incorrect clip installation are severe — not a gradual failure but a sudden, complete loss of termination under load.

A wire rope clip consists of a U-bolt and a saddle (bridge). The correct installation rule, universally taught in rigging courses and remembered as a mnemonic:

Additional clip installation requirements:

• Minimum number of clips: The number of clips required depends on rope diameter. General guidance: 3 clips for rope up to 19 mm; 4 clips for 20–25 mm; 5 clips for 26–32 mm. Always verify with the clip manufacturer's data — fewer clips than specified dramatically reduces holding capacity.
• Clip spacing: Space clips at a minimum of 6 rope diameters apart, measured between the U-bolt centres. Clips packed too closely together cannot develop the friction grip needed for rated holding capacity.
• Tightening torque: Clip nuts must be tightened to the manufacturer's specified torque — not "hand tight plus a bit". Under-tightened clips slip; over-tightened clips crush wires. Retighten after the initial load is applied — the rope will compress and seat under the first load, reducing nut tension.
• Dead end tail length: The tail beyond the last clip must extend at least 6 rope diameters past the clip to ensure adequate holding length.

Inspection and discard criteria

Wire rope and rigging equipment must be inspected before each use and formally inspected at regular intervals in accordance with AS4991 (lifting components) and the relevant equipment standard. The person performing the inspection must be competent to identify the defects listed below. Rigging hardware that fails inspection must be taken out of service immediately — not tagged for later assessment, not returned to the yard for review. Out of service means out of service.

Wire rope — discard when any of the following are present

• Broken wires: 6 or more broken wires in any one rope lay length in running rope (rope wound on drums or passing over sheaves); 3 or more broken wires in a single strand within one lay length. For slings, any broken wires in the eye or termination zone are cause for immediate discard.
• Kinks: Any kink — a permanent deformation where the wires have been displaced from their helical path — is a discard condition. Kinks cannot be straightened without permanently compromising the rope structure at that point.
• Birdcaging: A sudden release of load or a severe shock load can cause the strands to spring outward from the core, creating a birdcage appearance. Discard immediately.
• Corrosion: Surface rust on its own may not be cause for discard (lubricate and re-inspect), but pitting — corrosion that has penetrated below the wire surface — is a discard condition. Significant internal corrosion may not be visible externally; core-level corrosion is indicated by a rope that is stiffer than normal, dry, and discoloured when the strands are opened.
• Diameter reduction: A reduction in overall rope diameter of more than 3% from the nominal diameter indicates internal core failure or severe internal wear. Measure with a calliper at multiple points.
• Heat damage: Blue or straw discolouration of the wires indicates the rope has been exposed to temperatures that may have altered the wire's mechanical properties. Discard.

Synthetic slings — discard when any of the following are present

• Any cut, abrasion, or tear that penetrates the load-bearing fibres (not just the outer jacket)
• Burns or heat damage visible as glazed, melted, or charred fibres
• Chemical attack — stiffness, brittleness, or discolouration from exposure to acids, alkalis, or solvents
• Missing, illegible, or detached identification label (the tag is mandatory — a sling without a legible WLL tag must not be used)
• Knots — never tie a knot in a synthetic sling to shorten it; this creates a stress concentration and reduces capacity by 50% or more

Shackles — discard when any of the following are present

• Deformation of the bow — any visible bending or opening of the bow shape
• Wear on the pin or the inside of the bow exceeding 10% of the original diameter
• Cracks, gouges, or impact marks on the bow body
• Thread damage on screw pin shackles preventing full seating of the pin
• Missing cotter pin (split pin) on safety bolt shackles — never replace with wire or improvised locking methods
• No WLL marking — unrated shackles must not be used in lifting or rigging applications

Inspection tagging

All rigging equipment used in Australian industrial workplaces must be tagged and current. Colour coding for inspection tags follows a national cycle — the current colour indicates the equipment has passed inspection in the current period. Equipment with an out-of-date or missing tag must not be used, regardless of its apparent condition. The inspection tag confirms competent inspection, not just physical serviceability.

For transport applications — securing loads on flatbeds, trailers, and low loaders — chain tie-down systems with load binders are the heavy-duty alternative to synthetic webbing straps. Load binders apply rated tension across Grade 70 transport chain under the NHVR Load Restraint Guide 2025. See the Load Binder Guide for ratchet vs lever binder comparison, G70 chain sizing, and NHVR-compliant lashing calculations.

Frequently asked questions

What is the difference between WLL and SWL?

WLL (Working Load Limit) is the current Australian standard term for the maximum load a piece of rigging equipment is rated to carry under normal conditions. SWL (Safe Working Load) is the old term, removed from Australian Standard AS1418.1 in the 2002 revision. They describe the same concept — the maximum permissible working load, calculated by dividing the minimum breaking load by a design (safety) factor. For lifting equipment above the hook (the crane itself), the current term is Rated Capacity. Use WLL for all rigging hardware — slings, shackles, hooks, and lifting points.

What is a wire rope sling?

A wire rope sling is a length of wire rope with formed eyes at one or both ends, used to connect a load to a crane hook or other lifting device. The eyes are typically formed using a Flemish splice around a steel thimble, or by swaged ferrule, providing a rated connection point. Wire rope slings are available in single-leg, two-leg, three-leg, and four-leg configurations. The WLL of a multi-leg sling assumes a specific angle — always check the tag for the rated angle and derate if the actual rigging angle is shallower.

What is sling angle and why does it matter?

Sling angle is the angle between the sling leg and the horizontal. As the angle decreases (the sling legs spread further apart), the tension in each leg increases for the same total load. At 60° from horizontal, each leg of a two-leg bridle carries 15% more than it would at 90°. At 45°, it carries 41% more. At 30°, each leg carries the same tension as if it were supporting the entire load alone — two legs provide no additional capacity at this angle. Below 30°, the tension in each leg exceeds the load weight, and this configuration is prohibited in most Australian rigging standards. Always rig with sling angles above 30° and calculate the reduced WLL for any angle below 90°.

What is the difference between a D shackle and a bow shackle?

A D shackle (chain shackle) has a narrow, D-shaped bow designed for in-line loading only. It is strong in its intended direction but degrades rapidly under side loading. A bow shackle (anchor shackle) has a wider, rounded bow that can accept load from multiple directions and can accommodate multiple sling eyes. The bow shackle is the standard choice for crane lifting and multi-leg sling assemblies. D shackles are used for single-point in-line connections where the load direction is controlled. Never side-load a D shackle.

What is the difference between a screw pin and safety bolt shackle?

A screw pin shackle has a threaded pin that is wound in by hand — fast to connect and disconnect, suitable for frequent re-rigging. However, screw pins can rotate and unwind under vibration or load rotation. If used in vibrating or rotating applications, the pin must be moused (wired shut). A safety bolt (bolt-type) shackle has a smooth pin locked by a nut and cotter pin — it cannot unwind and is the required type for permanent installations, overhead lifts, and any application involving vibration or load rotation.

What does "never saddle a dead horse" mean in rigging?

It is a mnemonic for correct wire rope clip installation. The saddle (bridge) of the clip always bears on the live rope — the load-carrying section. The U-bolt always bears on the dead end (the short tail). Installing the saddle on the dead end crushes the load-bearing wires and dramatically reduces termination efficiency, creating a high risk of the tail pulling through under load. Every wire rope clip installation must follow this rule, plus the correct number of clips for the rope diameter (minimum three for most sizes) and the specified tightening torque.

How many wire rope clips do I need?

The minimum number of clips depends on rope diameter. As a general guide: 3 clips for wire rope up to 19 mm diameter; 4 clips for 20–25 mm; 5 clips for 26–32 mm. Always check the clip manufacturer's specification for the exact rope diameter in use — the manufacturer's data takes precedence. Clips must be spaced a minimum of 6 rope diameters apart and tightened to the specified torque. Retighten after the first load is applied, as the rope will compress and seat, reducing nut tension.

What is the difference between 6×19 and 6×36 wire rope?

Both designations describe 6-strand wire rope. 6×19 has 16–26 wires per strand — fewer, larger wires that make it stiffer and more abrasion-resistant but less flexible and less fatigue-resistant. It is the standard for lifting slings, pendants, and static applications. 6×36 has 27–49 wires per strand — more, finer wires that make it flexible and fatigue-resistant, suitable for running ropes on cranes, winches, and sheave systems where repeated bending is the primary demand. The finer wires in 6×36 are more susceptible to surface abrasion than 6×19.

What is IWRC in wire rope?

IWRC stands for Independent Wire Rope Core — a small wire rope that runs through the centre of the main rope, supporting the strands. IWRC provides superior crush resistance and maintains rope geometry under side loads and drum-winding pressure, adding approximately 7.5% to the rope's overall breaking strength compared to an equivalent fibre core rope. IWRC is the correct core type for crane hoist ropes, winch lines, and any application involving drum winding or significant side loading. Fibre core (FC) is more flexible and used in slings and light-duty applications where flexibility matters more than crush resistance.

When should I discard wire rope?

Discard wire rope immediately if you find: 6 or more broken wires in any one rope lay length (in running rope); 3 or more broken wires in a single strand within one lay; any kink (permanent bend deformation); birdcaging (strands sprung outward from the core); pitting corrosion below the wire surface; reduction in overall rope diameter exceeding 3% of nominal; or heat discolouration (blue or straw tint on the wires). In slings, any broken wires at the eye or termination zone are an immediate discard condition regardless of quantity.

Can I shorten a synthetic sling by tying a knot?

No. Tying a knot in a synthetic sling creates a severe stress concentration at the knot and reduces the sling's capacity by 50% or more — while the WLL tag still shows the unmodified rating. The correct way to shorten a sling is to use a shortening clutch, a connecting link, or a shackle to take up slack in the configuration. Synthetic slings with knots must be removed from service.

What Australian standards apply to lifting slings and rigging?

Key standards: AS3569 (steel wire ropes — product specification), AS1666 (wire rope slings), AS3637 (web slings), AS3776 (lifting components — shackles), AS2741 (shackles), AS4344 (chain slings), AS4991 (lifting components — general requirements), and AS1418.1 (cranes, hoists and winches — general requirements, which defines WLL and Rated Capacity). All rigging equipment used in Australian industrial workplaces must be inspected regularly by a competent person and tagged under the current colour code cycle.

AIMS Industrial stocks wire rope slings, synthetic web slings, chain slings, and rigging hardware including shackles, thimbles, wire rope clips, and swaged ferrules. For help selecting the right sling type, configuration, and WLL for your application, contact our team.