Shackles are the connectors that hold rigging together — the link between a sling and a hook, a chain and an anchor point, or two legs of a multi-leg lifting arrangement. Get the shackle right and the whole rig is sound. Get it wrong and you have a single-point failure at the most loaded part of the assembly.
In Australian industry, two types dominate: the bow shackle (also called an anchor shackle) and the D-shackle (also called a dee shackle or chain shackle). They look similar, they carry similar loads, but they are not interchangeable — and using the wrong one in the wrong situation is a genuine safety issue.
This guide covers both types in full: how they differ, which pin type to choose, what Grade S, Grade T and Grade M mean, how to read WLL ratings, Australian standard AS 3776, correct rigging technique, mousing, stainless versus galvanised, and inspection criteria. By the end you will know exactly which shackle you need and how to use it safely.
What Is a Shackle and How Does It Work?
A shackle is a U-shaped metal connector closed by a pin threaded through both ends of the U. The body forms the load-bearing loop; the pin closes the opening and locks the assembly together. Under load, the pin is in double shear — it is supported on both sides — making shackles extremely efficient for their weight.
The two ends of the shackle body are called the ears. The pin passes through both ears and is tightened (screw pin) or locked (safety pin) to secure the connection. The curved base of the U is called the bow on a bow shackle and the crown on a D-shackle. This is where the load sits when the shackle is under tension.
Shackles are rated by their Working Load Limit (WLL), which is the maximum load they are designed to carry under normal working conditions. In Australia, shackles used for lifting must comply with AS 3776 — the Australian Standard for shackles. All compliant shackles are marked with their WLL, the manufacturer's name or trademark, the material grade, and a traceability batch number.
Shackles are used across construction, mining, maritime, agriculture, manufacturing and general industrial rigging. They connect wire rope slings, chain slings, synthetic slings, hooks, eyebolts, turnbuckles and spreader bars into complete lifting assemblies.
For a full explanation of WLL, SWL, MBL and MRC — including how design factors are calculated, sling angle derating, and the weakest link rule — see our SWL vs WLL vs MBL Guide.
Bow Shackle vs D-Shackle: The Core Choice
The single most important shackle decision is whether to use a bow (anchor) shackle or a D (dee/chain) shackle. The difference is in the shape of the body, and that shape determines how the load is distributed and what rigging arrangements each type is suited to.
Bow Shackle (Anchor Shackle)
A bow shackle has a wide, rounded body — shaped like a capital D with an exaggerated curve, or like a pear. The wide bow allows multiple sling legs or fittings to sit side by side in the body without jamming or binding against each other. This makes the bow shackle the standard choice for multi-leg sling arrangements, where two or more sling legs connect to a single master link or hook via a shackle.
Because the bow is rounded rather than pointed, loads introduced from an angle are better distributed around the curve of the body rather than concentrated at a sharp corner. Bow shackles tolerate some degree of angular loading better than D-shackles, though side loading of any shackle must still be avoided.
Best for: multi-leg slings, connecting to master links, general lifting where multiple fittings must attach to the same point, anchor chain connections, and any application where the load may not always be perfectly in-line.
D-Shackle (Dee / Chain Shackle)
A D-shackle has a narrow, D-shaped body — the two legs of the U are closer together and the crown is smaller. This narrower profile is designed to accept a single load in a straight line — typically the end link of a chain, a single sling leg, or a hook. Because the body is narrow, the load sits squarely at the crown and the forces travel efficiently through the body to the pin.
D-shackles are stronger in pure in-line tension for a given pin diameter than bow shackles of the same nominal size, because the narrower body transmits load more directly. However, they must only carry a single point of attachment through the body. Placing two chain links or two sling eyes side by side in a D-shackle causes the links to ride up on the inside edges of the body — generating stress concentrations that are not accounted for in the WLL rating.
Best for: connecting a single chain link, a single wire rope end fitting, a single hook, or any application where the load is truly in-line with a single attachment point.
Bow vs D — Quick Reference
| Feature | Bow (Anchor) Shackle | D (Dee / Chain) Shackle |
|---|---|---|
| Body shape | Wide, rounded, pear-shaped | Narrow, D-shaped |
| Multiple fittings in body? | Yes — designed for this | No — single fitting only |
| In-line load efficiency | Good | Very good |
| Angular load tolerance | Better (rounded bow) | Lower (sharp crown) |
| Multi-leg sling connection | ✔ Preferred | ✘ Not recommended |
| Chain or single eye connection | ✔ Suitable | ✔ Preferred |
| Common AS 3776 sizes | 5 mm – 50 mm | 5 mm – 50 mm |
The rule of thumb: if more than one fitting goes into the body, use a bow shackle. If it is a single in-line connection, either will work — but a D-shackle is often more compact and lighter for the rated load.
Screw Pin vs Safety (Bolt) Pin Shackle
Once you have chosen bow or D, the next decision is the pin type. Shackles come in two primary pin configurations: screw pin and safety pin (also called bolt-type or round pin). The pin type determines how the shackle is secured and whether it is suitable for permanent or temporary rigging.
Screw Pin Shackle
The screw pin shackle has a pin that threads directly into the ear of the shackle body. To close the shackle, you thread the pin in by hand until it is tight, then back it off a quarter turn and align the hole in the pin with the hole in the ear so you can mouse it if required.
Screw pin shackles are the most common type in general industrial use. They are quick to rig and de-rig, which makes them ideal for temporary connections — a sling assembled at the start of a job and removed at the end. The major risk with screw pin shackles is unscrewing under load: vibration, rotation, and repeated cycling can cause the pin to unscrew, especially if the shackle is rotating in service (for example, connecting to a swivel or used in a rotating lift). If the pin backs out fully under load, the shackle can open.
To prevent unscrewing, the screw pin must always be moused (see the mousing section below) whenever the shackle is in a position where it could rotate, vibrate, or remain in service for an extended period. This is a mandatory requirement under AS 3776 for working arrangements.
Best for: temporary rigging, frequent assembly/disassembly, general lifting where the shackle is monitored and moused when appropriate.
Safety Pin (Bolt-Type) Shackle
A safety pin shackle uses a bolt that passes through both ears of the body and is secured by a nut — with a cotter pin (split pin) through the bolt to lock the nut in place. To close a safety pin shackle you push the bolt through, thread on the nut and tighten it, then insert the cotter pin and spread it.
Safety pin shackles cannot unscrew under load, vibration, or rotation. They are the required type for permanent or semi-permanent installations, for shackles that will be in service for extended periods, for applications with significant vibration, and for any rigging where the shackle may rotate. Safety pin shackles take longer to rig and de-rig, so they are less common in general lifting work but essential in any situation where a screw pin could work loose.
Best for: permanent or long-term installations, rotating applications, high-vibration environments (mining, marine, machinery), rigging that cannot be regularly inspected for pin tightness.
Screw Pin vs Safety Pin — Quick Reference
| Feature | Screw Pin | Safety (Bolt) Pin |
|---|---|---|
| Closure method | Threaded pin — hand-tightened | Bolt + nut + cotter pin |
| Risk of unscrewing | Yes — must be moused | No — nut locks in place |
| Assembly speed | Fast | Slower |
| Rotating/vibration use | Only if properly moused | ✔ Preferred |
| Permanent installation | ✘ Not recommended | ✔ Required |
| Temporary lifting | ✔ Standard choice | ✔ Suitable but slower |
Shackle Grades: What Grade S, T and M Mean
Shackle grade is one of the most misunderstood aspects of shackle selection. Grade refers to the material and mechanical properties of the shackle, not just its strength. In Australia, shackle grades under AS 3776 are defined as Grade S, Grade T and Grade M, and each has specific characteristics and applications.
Grade S — Standard Commercial Grade
Grade S is the most common shackle grade in Australian industrial and lifting applications. Grade S shackles are manufactured from carbon or alloy steel and are heat-treated to achieve the required mechanical properties under AS 3776. They are colour-coded blue on the pin for easy identification.
Grade S shackles are suitable for general overhead lifting and rigging. They have a defined proof load (typically 2× WLL) and a minimum breaking load (typically 6× WLL, giving a safety factor of 6:1 under AS 3776). This is the grade you will find at AIMS Industrial in the Austlift and Beaver ranges for general rigging use.
Grade S shackles are not suitable for use with higher-grade chain such as Grade 80 or Grade 100 chain systems, where the chain's WLL exceeds the shackle's capacity at the same size. In those systems you need Grade T or Grade M hardware to keep pace with the chain.
Grade T — High-Tensile (Alloy) Grade
Grade T shackles are manufactured from high-tensile alloy steel and are typically used in conjunction with Grade 80 chain systems. They are colour-coded yellow on the pin. Grade T shackles have a higher WLL for a given body size compared to Grade S, making them more compact for the rated capacity. They are the correct choice when connecting Grade 80 chain to Grade 80 fittings — a Grade S shackle at the same nominal size will typically be the weak link in the assembly.
Grade M — Grade 100 Alloy
Grade M shackles (also described as Grade 100 shackles) are manufactured from Grade 100 alloy steel and are designed for use with Grade 100 chain systems — the highest-strength chain in common lifting use. They are colour-coded purple (violet) on the pin. Grade M shackles deliver the highest WLL-to-weight ratio of the three grades and are the correct choice when building Grade 100 chain sling assemblies.
Grade Comparison Summary
| Grade | Material | Pin Colour | Chain System | Safety Factor (AS 3776) |
|---|---|---|---|---|
| Grade S | Carbon / alloy steel | Blue | General lifting / no chain system | 6:1 |
| Grade T | High-tensile alloy | Yellow | Grade 80 chain | 6:1 |
| Grade M | Grade 100 alloy | Purple / violet | Grade 100 chain | 6:1 |
Important: never mix grades within a chain sling assembly. The WLL of the assembly is limited by its weakest component. A Grade 100 chain connected to a Grade S shackle that is too small will fail at the shackle — the chain rating means nothing if the shackle can't keep up.
WLL Size Reference: Shackle Sizes and Rated Loads
Shackle WLL is determined by the pin diameter and body grade. The sizes below are typical values for Grade S bow and D-shackles under AS 3776. Always check the stamped WLL on the shackle body — this is the definitive rating, not a catalogue estimate.
| Pin / Body Size | Grade S Bow WLL | Grade S D-Shackle WLL | Typical Use |
|---|---|---|---|
| 5 mm | 0.5 t | 0.5 t | Light rigging, safety lines |
| 6 mm | 0.8 t | 0.8 t | Light loads, safety applications |
| 8 mm | 1.5 t | 1.5 t | General rigging, 1-leg slings to ~1 t |
| 10 mm | 2 t | 2 t | 2-tonne sling assemblies, single chain leg |
| 13 mm | 3.2 t | 3.2 t | Medium lifting, machinery, structural steel |
| 16 mm | 4.75 t | 4.75 t | Heavier lifts, multi-leg slings to 4 t |
| 19 mm | 6.5 t | 6.5 t | Large lifts, construction, mining |
| 22 mm | 8.5 t | 8.5 t | Heavy industry, offshore rigging |
| 25 mm | 12 t | 10 t | Heavy lifting, crane rigging |
| 32 mm | 17 t | 13.5 t | Very heavy lifts, crane and offshore |
Note: the WLL values above are representative of typical Grade S shackles. Exact values vary slightly between manufacturers. The stamped WLL on the shackle is always the authoritative rating. Never assume WLL from size alone — always read the marking.
Sizing rule: the shackle WLL must equal or exceed the maximum load it will carry in the actual rigging configuration — not just the weight of the load. In a two-leg sling at 60° included angle, each leg carries more than half the load weight due to the sling angle effect. Calculate the leg tension correctly before selecting your shackle size.
Australian Standard AS 3776 — Shackles
All shackles used for lifting in Australia should comply with AS 3776: Shackles for lifting. This standard specifies the design, materials, dimensions, mechanical properties, testing, and marking requirements for shackles used in lifting applications.
What AS 3776 Requires
AS 3776 requires that every compliant shackle is permanently marked with:
- The manufacturer's name, trademark, or registered mark
- The Working Load Limit (WLL) in tonnes
- The material grade (S, T, or M)
- A batch or heat number for traceability
Shackles must pass a proof load test at the manufacturing stage — typically 2× WLL — with no permanent deformation. Minimum breaking load requirements under AS 3776 establish a safety factor of 6:1 (six times the WLL before the shackle breaks under static test conditions).
What It Means in Practice
If a shackle is not marked — or the markings are unreadable — it must be removed from service. A shackle with no WLL stamp has an unknown load rating. It cannot be used for lifting because there is no basis for calculating whether it is appropriate for the task.
Shackles imported and sold in Australia as compliant must meet AS 3776 requirements. When purchasing, ask for a declaration of conformance or look for AS 3776 compliance stated on the product or packaging. The Austlift and Beaver shackles in the AIMS range are supplied as AS 3776 compliant.
Inspection Requirements
AS 3776 and the broader Australian rigging framework under Work Health and Safety regulations require that lifting equipment — including shackles — be inspected by a competent person before each use and periodically as part of a formal inspection regime. The frequency of formal inspection depends on the application and duty. In high-duty or harsh environments (mining, offshore, marine), inspection frequency is higher.
Records of inspection, including dates and any defects found, should be kept for all lifting equipment used in the workplace. This is especially important for shackles that are part of dedicated sling assemblies.
How to Rig a Shackle Correctly
Correct rigging technique is not just about connecting one thing to another — it is about ensuring load is transferred through the shackle the way it was designed to carry it. Poor rigging technique can reduce the effective WLL to a fraction of the rated value.
The Pin Must Be in the Fitting, Not the Bow
This is the most consistently violated shackle rigging rule. When connecting a shackle between a sling and a hook, the pin goes through the eye of the sling or hook, and the load sits in the bow (or crown) of the shackle. This is because the body carries load efficiently — the pin is in shear and is much weaker than the body under direct pull.
If the pin carries the load (the shackle is assembled the wrong way around), the effective WLL of the assembly is dramatically reduced — sometimes to less than 50% of the rated value. Always check orientation before lifting.
Load Must Be In-Line with the Shackle
Shackle WLL ratings assume the load is applied in-line — that is, the tension pulls squarely through the body from bow to pin. Side loading — where the load is applied at an angle to the plane of the body — can reduce the effective WLL by 50% or more depending on the angle. Both bow and D-shackles are rated for in-line loads only.
If your rigging arrangement generates side loads on a shackle (for example, a load block that swings out of line, or an anchor point on a sloped surface), you need a swivel or a cheek plate assembly — not a standard shackle in the wrong orientation.
Only One Load Per D-Shackle Body
As described in the bow vs D-shackle section: a D-shackle body is designed for a single fitting. Two chain links, two eyes, or one chain link and one sling eye placed side by side in a D-shackle body will cause the load to rock from side to side inside the body, generating bending loads in the body and in the fittings that are not accounted for in the WLL. If you need to connect multiple fittings at one point, use a bow shackle.
Screw Pin Must Be Fully Threaded
A screw pin must be fully threaded into the ear — all threads engaged — before use. A pin that is only partially threaded has a dramatically reduced load capacity. Hand-tighten the pin fully, then back off one quarter turn so the mousing hole aligns. Do not use tools to over-tighten the pin; doing so can damage the threads and make removal difficult after loading.
The Shackle Must Be the Right Size for the Fitting
The pin must fit the eye of the sling, hook, or chain link it passes through without being forced. A pin that is too large for the eye forces the eye open laterally as load is applied. A pin that is too small allows the eye to slide along the pin, concentrating load at one point. The eye of the fitting should slide over the pin freely but without excessive play.
Mousing a Shackle Pin
Mousing is the process of securing a screw pin so it cannot unscrew under load, vibration, or rotation. It is a mandatory safety step for any screw pin shackle that is in a working rigging arrangement — especially where the shackle may rotate or vibrate in service.
Why Mousing Matters
A screw pin that is not moused can unscrew progressively as the shackle rotates under load. Once the pin backs out enough that the threads disengage, the shackle opens and the load drops. This is not a theoretical risk — shackle pin backing is a documented cause of rigging failures in Australian workplaces. Mousing is simple and takes seconds. There is no excuse for not doing it.
How to Mouse a Shackle
The most common mousing method uses a single tie of mousing wire (soft iron seizing wire, typically 1.0–1.6 mm diameter):
- Thread the pin fully into the ear, then back off a quarter turn to align the mousing hole in the pin with the hole in the ear.
- Pass the mousing wire through the hole in the pin.
- Wrap the wire around the outside of the pin shank, then pass both ends through the hole in the ear (or loop around the ear lug).
- Twist the wire ends together firmly — 3 or 4 twists minimum — and tuck the twisted end back so it cannot snag.
The mousing wire does not need to be strong — it is not carrying load. Its job is simply to prevent the pin from rotating. A clean, tight mousing wire tie is sufficient. Do not use copper wire, cable ties, or tie wire of unknown composition as mousing — these may corrode, break, or fail to hold the pin securely over time. Use proper seizing wire.
For safety pin shackles: the cotter (split) pin through the bolt is the equivalent of mousing. Once the nut is tightened, the cotter pin must be inserted and spread to lock the nut. Never operate a safety pin shackle with a missing or unspread cotter pin.
Stainless Steel vs Galvanised Shackles
The AIMS shackle range includes both galvanised carbon steel shackles and 316 stainless steel shackles. Choosing between them is not a matter of preference — each has a specific application profile. For complete corrosion-resistant rigging, pair stainless shackles with matching stainless chain — see our Stainless Steel Link Chain Guide for 304 vs 316 grade selection, Grade 50 lifting chain to AS 4797, and calibrated marine anchor chain reference.
Galvanised Carbon/Alloy Steel Shackles
Hot-dip galvanised steel shackles are the standard industrial lifting shackle. Galvanising provides good corrosion resistance in general outdoor conditions and in mildly corrosive environments. Galvanised Grade S shackles are suitable for the vast majority of lifting and rigging applications in Australian industry: construction, manufacturing, mining (above-ground), agriculture, workshop, and general outdoor use.
Galvanised shackles are not suitable for:
- Marine or coastal environments with constant salt water exposure — the zinc coating degrades, exposing the underlying steel
- Chemical environments where the zinc reacts with the chemical present
- Food processing areas where carbon steel contamination is a risk
- Hygienic environments requiring non-ferrous materials
Note that galvanised shackles corrode from the inside out — the threads and the contact surfaces between the pin and ear corrode first, which is why pin seizure is a common issue with aged galvanised shackles in humid or outdoor environments. If a pin cannot be removed without tools, the shackle should be retired rather than forced open.
316 Stainless Steel Shackles
316 stainless steel (also called marine grade stainless) provides excellent resistance to salt water, mild acids, and corrosive chemicals. It is the standard material for marine rigging — yacht, commercial vessel, and offshore applications — as well as food processing, pharmaceutical, and chemical industry lifting.
Two important caveats for stainless shackles:
1. WLL is typically lower than the galvanised equivalent at the same nominal size. Stainless steel is less strong than alloy steel, and the WLL of a 316 SS shackle is typically 20–30% lower than a galvanised Grade S shackle of the same body dimension. Always read the WLL stamped on a stainless shackle — do not assume it equals the galvanised equivalent.
2. Stainless shackles are susceptible to galling. Galling is a form of surface damage that occurs when two stainless steel surfaces (the pin and the ear) are in contact under load and then rotated. The surfaces weld together momentarily and tear as they separate, causing rapid wear. To reduce galling risk, apply a small amount of anti-seize compound to the pin threads before assembly. Never use stainless shackles dry and then apply high torque to remove the pin — galling can make the pin impossible to remove without cutting.
Stainless vs Galvanised — When to Use Each
| Application | Galvanised Steel | 316 Stainless Steel |
|---|---|---|
| General industrial lifting | ✔ Preferred | Suitable but expensive |
| Outdoor / construction | ✔ Standard | Overkill for most uses |
| Marine / coastal saltwater | ✘ Corrodes | ✔ Required |
| Food processing / hygienic | ✘ Not suitable | ✔ Required |
| Chemical / corrosive environment | Check compatibility | ✔ Preferred (check grade) |
| High-strength lifting (Grade 80/100) | ✔ (matching grade) | ✘ Not suitable (strength) |
| Permanent outdoor installation | Monitor zinc coating | ✔ Lower maintenance |
Shackle Inspection and Discard Criteria
A shackle that looks intact can be at or beyond the end of its service life. Visual inspection before every use is mandatory, and any shackle that does not pass inspection must be removed from service immediately — tagged out, bent and rendered unusable, or destroyed. It must not be set aside for later use or put back in the rigging bag on the assumption someone else will deal with it.
Pre-Use Inspection Checklist
Before every lift, check each shackle in the assembly for the following:
Marking: The WLL and grade must be readable. If the markings are worn, corroded, or missing — retire the shackle. An unreadable WLL is an unknown WLL.
Body distortion: The shackle body must be symmetrical. Any elongation, twisting, spreading of the ears, or deformation of the bow or crown is a discard indicator. Shackle bodies that have been overloaded elongate visibly — the bow spreads and the body becomes longer. Even 2–3% elongation is significant and indicates overload.
Cracks and gouges: Any crack anywhere on the body or pin is an immediate discard. Cracks, even hairline surface cracks, indicate structural failure in progress. Gouges and nicks concentrate stress; deep gouges (greater than 10% of the body or pin cross-section) are a discard criterion.
Wear: The pin, the holes in the ears, and the bearing surfaces of the bow or crown all wear with use. Wear reduces the effective cross-section carrying the load. Wear exceeding 10% of the original diameter at any point is a discard criterion under most inspection standards. In practice, measure the pin diameter at the most worn point and compare to the nominal diameter.
Corrosion: Surface rust is acceptable on galvanised shackles when it is superficial (rust staining under the zinc, pitting of the zinc surface). Pitting of the underlying steel, especially in the threads or at the pin-ear interface, is a discard criterion. Corrosion that has reduced cross-section by 10% or more is a discard criterion.
Pin condition: The pin must be fully threaded and rotate freely (screw pin) or pass through the ears cleanly (safety pin). A pin that is bent, galled, or difficult to move should be discarded with the shackle. Never straighten a bent pin and reinstall it.
Thread condition: The threads must be clean and undamaged. Any stripping, cross-threading, or corrosion of the thread is a discard criterion. Do not lubricate threads with heavy grease or oil — this can mask thread damage. Use a light machine oil or anti-seize on stainless pins only.
After an Overload or Shock Load
Any shackle involved in a load incident — a dropped load, a snatch load, a rigging failure — must be removed from service and inspected by a competent person before it is returned to use. In most cases, overloaded shackles should be retired: the damage caused by overload is often internal (crystalline structure changes, micro-cracking) and not visible on the surface. If in doubt, retire it. A new shackle is always cheaper than an incident.
Discard Reference — Quick Guide
| Condition | Action |
|---|---|
| WLL / grade marking unreadable | Retire immediately |
| Any visible crack or fracture | Retire immediately |
| Body elongation or spreading visible | Retire immediately |
| Wear >10% at any load-bearing surface | Retire immediately |
| Corrosion pitting into base metal | Retire if >10% section loss |
| Bent or galled pin | Retire immediately |
| Involved in overload / incident | Inspect by competent person; likely retire |
| Pin cannot be removed without force | Retire (pin seizure = corrosion inside) |
AIMS Shackle Range: Austlift and Beaver
AIMS Industrial stocks shackles from two trusted Australian rigging brands: Austlift and Beaver. Both brands supply AS 3776 compliant shackles across a range of sizes, grades, and configurations for general industrial and marine applications.
Austlift Shackles
Austlift is one of Australia's leading rigging hardware suppliers, with a product range designed specifically for the Australian industrial and construction market. Austlift shackles in the AIMS range include:
- Grade S bow shackles — screw pin and safety pin, galvanised, from 6 mm (0.8 t WLL) to 32 mm and beyond
- Grade S D-shackles — screw pin and safety pin, galvanised, matching size range
- 316 stainless bow and D-shackles — for marine and corrosive environment applications
Austlift shackles carry full AS 3776 marking: WLL, grade, manufacturer mark, and batch traceability. They are backed by Austlift's engineering documentation and are suitable for use in certified rigging assemblies.
Beaver Shackles
Beaver is another well-established Australian brand in the rigging and lifting hardware market. Beaver shackles are known for consistent quality and are supplied with AS 3776 compliance documentation. The AIMS Beaver range includes galvanised Grade S bow and D-shackles in standard industrial sizes, as well as 316 stainless options for marine and hygienic applications.
Both brands are available through AIMS Industrial for trade and commercial customers. See the AIMS shackle collection for current stock and pricing.
For related rigging hardware, the AIMS range also covers wire rope slings, chain blocks, electric hoists, and turnbuckles — the full range of components needed to build compliant rigging assemblies.
Shackle Selection Checklist
Use this checklist to confirm you have the right shackle before you rig:
| # | Check | Detail |
|---|---|---|
| 1 | Calculate the actual load on the shackle | Account for sling angle, dynamic factors, and multi-leg effects — not just the gross weight |
| 2 | Select the correct WLL | Shackle WLL must equal or exceed the calculated load on that shackle position |
| 3 | Choose bow or D based on the attachment | Multiple fittings in body → bow shackle. Single fitting → either (bow or D) |
| 4 | Choose screw pin or safety pin | Temporary / monitored → screw pin (moused). Permanent / vibrating / rotating → safety pin |
| 5 | Confirm the grade matches the chain or sling system | Grade S for general lifting. Grade T for Grade 80 chain. Grade M for Grade 100 chain |
| 6 | Choose galvanised or stainless | Galvanised for general industrial. 316 SS for marine, food, or chemical environments |
| 7 | Confirm the pin fits the eye of the fitting | Must pass through freely without forcing — no excessive play |
| 8 | Check AS 3776 markings are readable | WLL, grade, and maker's mark must be visible and legible |
| 9 | Inspect the shackle — body, pin, threads | No cracks, deformation, excessive wear, or corrosion pitting |
| 10 | Rig correctly — pin in the fitting, load in the bow | Never put the load on the pin. Ensure load is in-line |
| 11 | Mouse the screw pin (or fit cotter pin on safety pin) | Mousing wire through pin hole, tied to ear. Cotter pin spread |
| 12 | Check the whole assembly before lifting | All shackles closed, moused, correctly oriented, correct WLL for their position |
Frequently Asked Questions: Bow Shackles and D-Shackles
What is the difference between a bow shackle and a D-shackle?
A bow shackle (anchor shackle) has a wide, rounded body that can accommodate multiple fittings side by side — it is the standard choice for multi-leg sling assemblies and anywhere more than one fitting connects at one point. A D-shackle (dee or chain shackle) has a narrow, D-shaped body designed for a single in-line fitting such as the end link of a chain. Both are rated by WLL and comply with AS 3776 in Australia, but they are not interchangeable for multi-point connections.
What does WLL mean on a shackle?
WLL stands for Working Load Limit. It is the maximum load the shackle is designed to carry under normal working conditions. The WLL is stamped directly on the shackle body and must be clearly readable before use. Under AS 3776, Grade S shackles have a minimum breaking load of six times the WLL — the safety factor built into the design. The WLL assumes the load is applied in-line; side loading reduces the effective WLL significantly.
What does Grade S mean on a shackle?
Grade S is the standard commercial lifting grade for shackles under AS 3776. Grade S shackles are manufactured from carbon or alloy steel, heat-treated to required mechanical properties, and colour-coded blue on the pin. They are suitable for general overhead lifting and rigging. Grade T (yellow pin) is for Grade 80 chain systems and Grade M (purple pin) is for Grade 100 chain systems. Within a rigging assembly, all components must be the same or compatible grade — a Grade S shackle in a Grade 100 chain assembly will be the weak point.
Can I use a bow shackle for a multi-leg sling?
Yes — a bow shackle is the correct choice for connecting multiple sling legs at a single point, such as connecting a 2-leg or 4-leg chain or wire rope sling to a crane hook via a master link and shackle. The wide rounded bow allows multiple fittings to sit side by side without jamming. A D-shackle must not be used for this purpose — its narrow body forces multiple fittings to ride up on the inside edges of the body, generating stresses not accounted for in the WLL rating.
What is the difference between a screw pin and a safety pin shackle?
A screw pin shackle has a pin that threads into the ear — fast to assemble but can unscrew under vibration or rotation unless moused (secured with seizing wire through the pin hole). A safety pin shackle uses a bolt with a nut and cotter pin — slower to assemble but cannot unscrew. Screw pin shackles suit temporary lifting work where the shackle is assembled, used, and then broken down. Safety pin shackles are required for permanent installations, high-vibration applications, and any connection where the shackle may rotate in service.
How do I mouse a shackle pin?
To mouse a screw pin shackle: thread the pin fully, then back it off a quarter turn until the hole in the pin aligns with the hole in the ear. Pass a length of soft iron seizing wire (1.0–1.6 mm) through the pin hole, wrap it around the pin shank, then pass both ends through or around the ear lug and twist them together tightly — three to four twists minimum. Tuck the twisted end back so it cannot snag. The mousing wire does not carry load — its job is purely to prevent the pin from rotating and unscrewing. Use proper iron seizing wire; not cable ties or copper wire.
Can a stainless steel shackle be used for overhead lifting?
Yes, but with two caveats. First, the WLL of a 316 stainless steel shackle is typically 20–30% lower than a galvanised Grade S shackle of the same nominal body size — always read the WLL stamped on the shackle, never assume it equals the galvanised equivalent. Second, stainless shackles are susceptible to galling (the pin can seize in the ear under load) — apply a small amount of anti-seize compound to the pin threads before assembly to reduce this risk. Stainless shackles are the correct choice for marine, food processing, and corrosive environments where galvanised steel would corrode.
What Australian Standard applies to lifting shackles?
The relevant Australian Standard is AS 3776: Shackles for lifting. It specifies design, materials, mechanical properties, testing (including proof load at 2× WLL), minimum breaking load (6× WLL, giving a 6:1 safety factor), and mandatory marking requirements — WLL, grade, maker's mark, and batch number. All shackles used for lifting in Australian workplaces should comply with AS 3776. A shackle with no legible AS 3776 markings cannot be used for lifting — its WLL is unknown.
How do I inspect a shackle before use?
Before every lift, check: WLL and grade markings are readable; the body is symmetrical with no elongation or spreading of the ears; there are no cracks, fractures, or deep gouges; wear at the pin, ears, and crown is less than 10% of the original diameter; corrosion has not caused pitting into the base metal beyond 10% section loss; the pin moves freely, is undamaged, and the threads are clean. Any shackle failing any of these checks must be removed from service immediately — tagged, bent, or destroyed so it cannot be reused.
Can a shackle be used sideways (side-loaded)?
No. The WLL rating of both bow and D-shackles assumes the load is applied in-line — pulling squarely through the body from bow to pin. Side loading, where the force is applied at an angle to the plane of the shackle body, can reduce the effective WLL by 50% or more depending on the angle. If your rigging arrangement generates persistent side loads on a shackle, you need a different solution — a swivel, a cheek plate, or a redesigned anchor point — not a standard shackle operating out of its intended plane.
How do I choose the right size shackle for my sling?
First calculate the actual load on the shackle — this is not just the gross weight of the load. For a two-leg sling at 60° included angle, each leg carries more than half the load weight due to the sling angle effect; the shackle must handle that leg tension. Select a shackle with a WLL equal to or greater than the calculated leg load. Then confirm the pin fits the sling eye or chain link it must pass through — freely but without excessive play. If in doubt, size up. A shackle that is slightly oversized is safe; one that is undersized is not.
What is the load limit if I put the load on the pin instead of the bow?
Significantly less than the stamped WLL — often 50% or below, depending on the pin diameter and shackle design. The shackle body is designed to carry the load; the pin is in double shear and is much weaker in direct tension than the body. When a shackle is assembled the wrong way around — pin carrying the load, fitting in the bow — the effective WLL of the assembly is dramatically reduced. Always orient the shackle so the load sits in the bow (or crown) of the body, with the pin passing through the eye of the sling, hook, or fitting.
For complementary rigging hardware, also see the AIMS Swivels range — used with shackles in rigging assemblies to prevent rope and sling twist. For the pins that connect clevis brackets, rod ends, and yokes in your rigging assemblies, see our Clevis Pin Guide.