This page provides engineering reference data for Grade 4 forged steel eyebolts to BS EN ISO 3266:2010+A1:2015. The standard specifies general characteristics, performance requirements and critical dimensions required for interchangeability and compatibility with other lifting components.
These eyebolts are designed for general lifting purposes and may be used for both axial and inclined loading, subject to the loading conditions and working load limits specified for the particular installation.
The principal dimensions used by BS EN ISO 3266 are:
The following table gives the principal dimensions and axial working load limits for Grade 4 forged steel eyebolts to BS EN ISO 3266.
| Thread Size | Axial WLL (tonnes) |
Dimensions (mm) | |||||
|---|---|---|---|---|---|---|---|
| E min. |
H max. |
F min. |
r min. |
B min. |
s min. |
||
| M8 | 0.20 | 9 | 12 | 6 | 1 | 17 | 2 |
| M10 | 0.32 | 11 | 15 | 8 | 1 | 20 | 3 |
| M12 | 0.40 | 13 | 18 | 9 | 1 | 21 | 3 |
| M16 | 0.80 | 18 | 24 | 13 | 1 | 28 | 4 |
| M20 | 1.60 | 25 | 30 | 18 | 1 | 38 | 5 |
| M24 | 2.50 | 32 | 36 | 22 | 2 | 46 | 6 |
| M30 | 4.00 | 40 | 45 | 28 | 2 | 57 | 8 |
| M36 | 6.30 | 50 | 54 | 35 | 3 | 70 | 9 |
| M42 | 8.00 | 57 | 63 | 40 | 3 | 79 | 11 |
| M48 | 10.00 | 63 | 72 | 44 | 3 | 87 | 12 |
| M52 | 12.50 | 71 | 78 | 49 | 3 | 97 | 13 |
| M56 | 16.00 | 80 | 84 | 56 | 4 | 109 | 14 |
| M64 | 20.00 | 89 | 96 | 63 | 4 | 121 | 16 |
| M72 × 6 | 25.00 | 100 | 108 | 70 | 4 | 135 | 18 |
| M80 × 6 | 32.00 | 113 | 120 | 79 | 4 | 152 | 20 |
| M90 × 6 | 40.00 | 126 | 135 | 89 | 5 | 169 | 23 |
| M100 × 6 | 50.00 | 141 | 150 | 99 | 5 | 189 | 25 |
WLL is the working load limit for loading along the centreline axis of the eyebolt. Inclined loading requires separate consideration and the axial WLL must not simply be assumed to apply.
The eyebolt shank threads are metric ISO threads. For sizes up to M64 the standard uses the appropriate ISO coarse-pitch thread. The larger sizes M72, M80, M90 and M100 use a 6 mm pitch.
The threaded shank, collar and supporting threaded hole form part of the lifting load path. Correct thread form, engagement length and supporting material are therefore essential when installing an eyebolt.
BS EN ISO 3266 distinguishes between:
The WLL in the dimensional table is the axial working load limit. An eyebolt selected for inclined loading must be assessed using the loading conditions specified by the standard and the manufacturer's information.
The underside of the eyebolt collar must seat correctly against the supporting surface. The standard requires the underside of the collar to be machined in alignment and at right angles to the shank axis so that the load can be transmitted correctly into the supporting component.
The installation should ensure that:
One purpose of the dimensional requirements in BS EN ISO 3266 is to provide compatibility with other standard lifting components.
The standard specifies eye dimensions that permit direct connection with shackles having the same working load limit in accordance with ISO 2415. Larger-eye designs may also permit direct connection with suitable sling hooks of comparable working load limit.
Compatibility should not be judged solely from whether a hook or shackle physically fits through the eye. The geometry and working load limits of the connected components must also be suitable for the lifting arrangement.
BS EN ISO 3266 Grade 4 eyebolts are specified for general use over the temperature range:
−20°C to +200°C
For service outside this temperature range, the eyebolt manufacturer should be consulted.
An eyebolt conforming to BS EN ISO 3266 is a forged lifting component rather than an ordinary threaded eye fastener. The eye and shank are forged as one piece and the finished component is subject to specified material, heat-treatment, mechanical test and manufacturing proof-test requirements.
The standard also provides for identification and traceability of the component. When assessing an installed lifting point, markings and traceability should therefore be considered together with dimensions and condition.
BS EN ISO 3266 superseded the withdrawn British Standard BS 4278:1984. RoyMech retains the BS 4278 pages separately because those dimensions and safe working loads remain useful when identifying or maintaining older equipment.
The BS 4278 data should not be mixed with BS EN ISO 3266 dimensions or working load limits. When an existing eyebolt is being assessed, first identify the standard and type to which it was manufactured.
| Reference | Status / Application |
|---|---|
| BS EN ISO 3266:2010+A1:2015 | Current UK standard – Grade 4 forged steel eyebolts for general lifting purposes |
| BS 4278:1984 | Withdrawn – retained by RoyMech as a legacy engineering reference |
At the time this page was prepared, BS EN ISO 3266:2010+A1:2015 remains the current UK adoption of ISO 3266 and is under review.
ISO 3266:2010 was reviewed and confirmed in 2026. A new edition is under development but has not yet replaced ISO 3266:2010. This RoyMech page should therefore continue to reference the published 2010 standard and its 2015 amendment until the replacement standard is issued.