A shackle is usually the smallest component in a lifting assembly and the one most often chosen carelessly. It carries everything. This page sets out the two decisions that matter — shape and pin — and the mistakes that reduce a shackle's capacity before you even load it.
Start with the shape: D-shackle or bow shackle
A D-shackle (also called a dee shackle or chain shackle) has a narrow, straight-sided body. The narrow profile keeps the load aligned along the pin axis, which is what you want for a single, straight pull — one chain leg, one sling, one direction.
A bow shackle (also called an anchor shackle) has a wide, rounded bow. That extra width lets you bring two or more sling legs into one point, and it tolerates loading from slightly varying angles better than a D-shackle does.
The rule of thumb used across the trade: one connection in one direction → D-shackle. Two or more legs meeting at one point → bow shackle.
| D-shackle (dee / chain) | Bow shackle (anchor) | |
|---|---|---|
| Body shape | Narrow, straight-sided | Wide, rounded bow |
| Single straight pull | Preferred | Works, but bulkier than needed |
| Two or more legs in one body | Not suitable | Designed for this |
| Tolerance of angular loading | Lower | Better |
| Weight and cost | Lower | Higher |
Then the pin: screw pin or bolt type
A screw pin threads directly into the ear of the body. It is fast to fit and remove, which makes it the right choice for connections you make and break regularly. The known risk is that vibration, rotation or repeated cycling can work the pin loose — if the shackle can rotate in service, or stays in place for a long period, the screw pin must be secured (moused) or a bolt type used instead.
A bolt type (safety pin) passes a bolt through both ears and secures it with a nut plus a split cotter pin. It cannot unscrew under vibration or rotation. It is slower to rig, and that is the trade you accept for permanent or semi-permanent installations, vibrating machinery, vehicles and marine use.
| Screw pin | Bolt type (safety pin) | |
|---|---|---|
| Fitting speed | Fast — hand or spanner | Slower — nut and cotter pin |
| Can it work loose? | Yes, under vibration or rotation | No — mechanically locked |
| Typical use | Temporary rigging, frequent changes | Permanent or long-term, vibration, rotation |
| Best when | You open it several times a day | It stays in place for weeks |
Side loading: the mistake that halves the capacity
A shackle is rated for load acting along the centre line of the body, with the load shared across the full width of the pin. Loading it sideways — so the pin acts as a hinge — concentrates the force on one leg and the pin.
Published guidance puts the effect bluntly: side loading can cut the working load limit by half or more. If your geometry pulls sideways, use a bow shackle, reposition the connection, or use spacers to centre the load on the pin.
- Never fit a pin from one shackle into the body of another, even if it threads in. Pin and body are manufactured and rated as a matched pair.
- Fully seat the pin every time. A partly seated pin carries a fraction of the rated load.
- Do not force, hammer or wedge a shackle into position.
- Avoid shock loading.
- Do not replace the pin with a standard bolt.
Working load limit follows the body diameter
WLL is governed by the body diameter, not by the pin size alone. For forged steel shackles of the common grade, published tables give roughly the following progression — treat it as an indication of the shape of the curve, and always read the marking on the actual shackle you are holding:
| Body diameter | Typical WLL |
|---|---|
| 6.5 mm | 0.33 t |
| 8 mm | 0.5 t |
| 10 mm | 0.75 t |
| 13 mm | 1.5 t |
| 16 mm | 2 t |
| 20 mm | 3.25 t |
| 22 mm | 4.75 t |
| 25 mm | 6.5 t |
| 32 mm | 9.5 t |
| 35 mm | 12.5 t |
Check these four things before every lift
- Body deformation — any widening or bending means the shackle has been overloaded. Take it out of service.
- Pin thread — damaged threads stop the pin seating fully.
- Wear at the crown — the inside of the bow wears where the sling or chain bears. Measure if you are in doubt.
- Markings — if the WLL and manufacturer marking are no longer legible, the capacity cannot be verified.
Shackles are inexpensive relative to what they carry. Replace them well before they become marginal.
Frequently asked questions
Which shackle is most commonly used in day-to-day rigging?
In general lifting and pick-and-place work, the screw pin bow (anchor) shackle is the most widely used, because it combines versatility with fast assembly. For a strictly in-line pull in a tight space, a D-shackle is often the more compact choice.
Can I put two sling legs in a D-shackle?
No. A D-shackle is intended for a single fitting in line with the pull. Placing two links or eyes side by side makes them ride up on the inside edges of the body, creating stress concentrations that the WLL does not account for. Use a bow shackle.
When must I use a bolt type shackle instead of a screw pin?
Whenever the connection is permanent or semi-permanent, exposed to vibration or rotation, or cannot be checked regularly. A screw pin can work loose under those conditions; a bolt type with a nut and cotter pin cannot.
What is the relevant European standard for lifting shackles?
EN 13889 covers forged steel shackles for lifting purposes. Shackles intended for lifting carry permanent markings — WLL, manufacturer identification and traceability — and, where required, CE marking.
How much does side loading reduce the capacity?
Published guidance states side loading can reduce the working load limit by half or more, because the load is no longer shared across the full pin width. Centre the load on the pin, or select a bow shackle for the geometry you have.
EN 13889: what has to be marked on the shackle itself
A shackle carries its rating on the steel, not only on the paperwork. EN 13889:2003+A1:2008 fixes exactly what goes where — on the body, and on the pin, which has its own separate requirements.
| Marked on | Must include | Why |
|---|---|---|
| Shackle body | Working load limit in tonnes (e.g. WLL 4,75); grade number 6; manufacturer's name, symbol or code; traceability code | All four are mandatory. The marking must be legible and indelible, and must not impair the mechanical properties of the shackle — in practice that rules out any marking method that heats or work-hardens the steel. |
| Pin, 13 mm diameter and above | Grade number 6; traceability code; manufacturer's symbol | Pins at or above this diameter carry their own separate marking requirement. The size threshold exists because thinner pins have too little surface to hold three legible marks without weakening the thread. |
| Pin below 13 mm | At least either the grade number or the traceability code | Reduced requirement for small pins, for the same reason. |
What a material certificate should contain
Where a certificate is required, the field list is fixed. These are the fields EN 13889 expects a mill test document to carry.
| Field | Content |
|---|---|
| Manufacturer identity | Name and address of the manufacturer or its authorised representative, with date of issue and authentication. |
| Standard | The number of the European standard the product is made to. |
| Traceability code | The code that ties this certificate to the actual units supplied. |
| Product description | Quantity and description of the shackles covered. |
| Grade | The grade number — 6 for EN 13889. |
| Working load limit | In tonnes. |
| Proof force | The manufacturing proof force, in kilonewtons. Note this is a different number from the WLL, and from the breaking force. |
| Breaking force confirmation | Confirmation that the specified minimum breaking force was met or exceeded. |
| Quality system | Identification of the EN ISO 9001 quality system, where in place and operating. |
Eight misuses that remove the margin
These are the failure modes that leave a shackle looking serviceable while it no longer is. Several of them are field alterations rather than selection errors, and they are the reason a shackle is treated as a rated component rather than as hardware.
| Misuse | What it does | Instead |
|---|---|---|
| Using a D-shackle with two sling legs | The two legs ride up on the inside edges of the body. The load concentrates on the pin in a way the rating does not cover. | Use a bow shackle. A D-shackle takes a single fitting in line with the pull. |
| Replacing the pin with a standard bolt | A general bolt has an unknown strength and is not heat-treated or dimensioned to match the body. This is the single most dangerous field alteration on a shackle. | Use only the matching pin supplied with, or specified for, that shackle body. |
| Side loading a shackle | Halves the capacity or more. The load stops being shared across the pin width and concentrates on one leg. | Centre the load on the pin, use a bow shackle, or fit spacers to align the pull. |
| Standing a shackle in line with a hook shank | The hook's load path bears on the shackle at an angle rather than through the bow, and the rating assumes the bow. | Connect to the bow, not to the standing part. Check the shackle is free to swing into line. |
| Field drilling, welding or grinding on the shackle | Any of these voids the manufacturer's rating for that component. | Never modify a rated component. If the geometry does not fit, change the hardware rather than the part. |
| Reusing a shackle with a distorted bow or worn crown | Deformation or crown wear means the body has been overloaded or the connection has been side loaded. | Remove it from service and replace it. Do not evaluate a worn shackle by eye alone — measure against the manufacturer's dimensions. |
| Leaving a screw pin shackle on a permanent connection | Vibration and rotation work the pin loose. A loosened pin is no longer fully seated and carries a fraction of the rated load. | Use a bolt type shackle with nut and cotter pin for permanent or unattended connections, and check it on a defined schedule. |
| Using a lifting-rated shackle for personnel or offshore work | These are outside the scope of general rigging standards and are governed by specific national legislation. | Treat personnel lifting as a different category of equipment entirely, certified for that purpose. |
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