This guide helps engineers select the appropriate RoyMech reference for lifting eyebolts and shackles. It explains the principal component types, loading arrangements and selection considerations before linking to the detailed dimensional and working-load data.
RoyMech contains both current-standard and legacy-standard lifting equipment data. Current-standard pages should normally be used when specifying new equipment. The legacy pages remain available for identifying, maintaining and assessing older equipment.
| Requirement | Recommended RoyMech Reference |
|---|---|
| New or current forged steel threaded lifting eyebolt | Forged Steel Eyebolts to BS EN ISO 3266 |
| New or current Dee or bow shackle | Forged Steel Shackles – BS EN 13889 / ISO 2415 |
| Existing BS 4278 collar eyebolt | Collar Eyebolts to BS 4278:1984 |
| Existing BS 4278 dynamo eyebolt | Dynamo Eyebolts to BS 4278:1984 |
| Existing BS 4278 eyebolt with link | Eyebolts with Link to BS 4278:1984 |
| Existing large bow shackle to older British Standards | Large Bow Shackles to BS 3032 / BS 6994 |
| Existing large Dee shackle to older British Standards | Large Dee Shackles to BS 3032 / BS 6994 |
The first question is whether the component is being specified for a new application or whether an existing lifting component or machine is being identified or assessed.
For new forged steel eyebolts, start with the current BS EN ISO 3266 reference.
For current forged Dee and bow shackles, use the BS EN 13889 / ISO 2415 reference.
Current Forged Steel EyeboltsOlder machinery may contain eyebolts and shackles manufactured to withdrawn British Standards such as BS 4278, BS 3032 and BS 6994.
RoyMech retains these dimensions and load tables because they can be valuable when identifying or maintaining older equipment.
Legacy Lifting ReferencesAn eyebolt normally provides a threaded lifting attachment to a machine, structure or component. A shackle provides a detachable connection between lifting components.
A typical lifting arrangement may therefore contain both: an eyebolt attached to the item being lifted and a shackle connecting that lifting point to a sling or other lifting component.
An eyebolt should not be selected from its thread diameter alone. The thread primarily establishes how the component is attached; it does not by itself establish the lifting capacity.
Selection should consider:
The direction of load is particularly important with eyebolts.
An axial load acts substantially along the centreline of the threaded shank. An inclined load acts at an angle to that axis and can introduce additional stresses into the eye, collar, shank and threaded connection.
A WLL quoted for axial loading should therefore not automatically be used for an inclined lifting arrangement.
The older BS 4278 standard illustrates particularly well why apparently similar lifting eyes cannot simply be treated as interchangeable.
RoyMech retains three separate BS 4278 references because their permitted applications differ.
A collar eyebolt incorporates a substantial collar which seats against the supporting surface. The collar assists in transmitting loads into the supporting component.
BS 4278 permitted specified inclined-loading arrangements for these eyebolts, subject to reduced loads and loading-direction requirements.
For an existing BS 4278 component see: Collar Eyebolts to BS 4278:1984 .
The legacy dynamo eyebolt is fundamentally an axial-lifting component.
BS 4278 warns that even a small departure from axial loading can produce undesirable stresses in the screw thread and shank. Where several dynamo eyebolts are used together, the lifting arrangement must maintain axial loading at each eyebolt.
See: Dynamo Eyebolts to BS 4278:1984 .
The BS 4278 eyebolt with link was intended as a more general-purpose lifting arrangement where the direction of load could not necessarily remain in the plane of a conventional eye.
The link provides articulation between the eye and sling connection, but permitted loads still depend upon the angle of loading.
See: Eyebolts with Link to BS 4278:1984 .
Shackles provide detachable connections between lifting components. Selection starts with the required WLL but must also consider the geometry of the connection and the direction in which the shackle will be loaded.
Important considerations include:
A Dee shackle has a relatively narrow body and is generally suited to connections where the load is substantially aligned with the centreline of the shackle.
It is a useful compact connection where large internal clearance is not required.
A bow shackle has a wider rounded body which provides greater internal clearance and can accommodate wider connections or more than one sling component where the permitted lifting arrangement allows it.
The larger bow does not mean that unrestricted side loading is permissible.
Shackles should be loaded in the manner for which they were designed. Poor alignment can introduce bending, spreading or other stresses that are not represented by the normal in-line WLL.
The pin should seat correctly and the connected components should not force the shackle body apart.
Where sling legs or other components impose angular loading, use the permitted loading arrangements and any WLL reductions specified by the manufacturer or applicable standard.
Older RoyMech lifting tables frequently use the term Safe Working Load (SWL), while current lifting component standards commonly use Working Load Limit (WLL).
WLL is the maximum load assigned to a lifting component by its manufacturer or standard under specified conditions. SWL is historically used for the load considered safe for a particular item or installation under its conditions of use.
When using legacy tables, retain the terminology used by the applicable standard rather than simply relabelling historical SWL data as modern WLL.
The weight being lifted is not necessarily the load carried by each sling leg or lifting point. Sling geometry affects the tension in each leg.
For a symmetrical two-leg arrangement where each sling leg is at an angle θ from the vertical, the idealised tension in each leg is:
where:
As the sling legs move further from the vertical, the tension in each leg increases.
| Angle from Vertical | Leg Tension as Fraction of Total Load W |
|---|---|
| 0° | 0.500 W |
| 30° | 0.577 W |
| 45° | 0.707 W |
| 60° | 1.000 W |
This simple relationship is useful for understanding sling geometry, but actual lifting arrangements must also account for load distribution, component ratings, permitted sling angles and the applicable lifting equipment requirements.
For a threaded eyebolt, the tapped hole and supporting component are part of the load path. A correctly rated eyebolt does not guarantee a correctly rated lifting point if the receiving thread or supporting material is inadequate.
Check:
Dimensions are useful when identifying old equipment, but dimensional similarity alone does not prove a lifting rating.
Where possible, establish:
Lifting components should be inspected in accordance with the applicable requirements and examination regime. Conditions requiring attention include:
Withdrawn standards do not automatically make existing engineering data useless. Older lifting components remain installed on machinery and equipment, and their original dimensional and load data can be important when identifying or assessing them.
RoyMech therefore retains the following legacy references separately from the current-standard pages.
Legacy dimensions and safe working loads for collar eyebolts to BS 4278:1984.
Collar Eyebolt ReferenceLegacy axial-lifting dynamo eyebolt dimensions and safe working loads to BS 4278:1984.
Dynamo Eyebolt ReferenceLegacy dimensions and safe working loads for the BS 4278 general-purpose eyebolt-with-link arrangement.
Eyebolt with Link ReferenceLegacy large bow shackle dimensions and load data to BS 3032:1958 and BS 6994:1988.
Legacy Bow Shackle ReferenceLegacy large Dee shackle dimensions and load data to BS 3032:1958 and BS 6994:1988.
Legacy Dee Shackle ReferenceCurrent Grade 4 forged steel eyebolt reference based on BS EN ISO 3266, including dimensions, WLL and loading considerations.
Forged Steel EyeboltsCurrent Dee and bow shackle reference covering BS EN 13889 and ISO 2415, including dimensions, WLL, grades and selection considerations.
Forged Steel ShacklesFor new lifting equipment, begin with the current BS EN ISO 3266 eyebolt or BS EN 13889 / ISO 2415 shackle references. Use the legacy BS 4278, BS 3032 and BS 6994 pages when identifying, maintaining or assessing equipment manufactured to those earlier standards.
Whatever standard applies, selection should be based on the complete lifting arrangement rather than component size alone. Consider load magnitude, direction, sling geometry, connection geometry, supporting structure, component identification and condition before establishing suitability.