Eye Bolt Guide: Types, WLL, Angle Loading & Safe Selection

2. Types of Eye Bolts: A Complete Overview — Quick Reference

The term "eye bolt" covers a wide family of fasteners. Not all of them are rated for lifting, and those that are rated carry very different capacities depending on type and load direction.

1. What Is an Eye Bolt?

An eye bolt is a threaded fastener with a closed circular loop — the eye or ring — formed at one end instead of a conventional head. The loop provides an attachment point for hooks, shackles, D-rings, wire rope slings, chain slings, or rigging hardware. The shank is threaded for some or all of its length and screws into a tapped hole in the load or through a clearance hole with a nut on the back face.

Eye bolts are used across Australian industry for:

• Lifting and hoisting machinery, motors, pumps, and fabricated assemblies
• Rigging permanent anchor points to structures, beams, and frames
• Tethering and restraint applications where a fixed anchor is required
• Suspended equipment mounting (lighting gantries, cable management runs, HVAC units)

A typical lifting eye bolt has three functional parts: the shank (the threaded portion that enters the parent material), the shoulder or collar (a flange that bears against the face of the parent material and is critical for angular load distribution), and the eye (the ring through which the sling hook or shackle pin passes). The presence and condition of that collar is the single most important variable in determining what a given eye bolt can safely do.

Eye bolts are covered by several international standards used in Australia. DIN 580 governs plain forged eye bolts; BS 4278 governs collared (shouldered) lifting eye bolts and defines their angular capacity; AS 4991 (Lifting Components) references eye bolts in the context of the broader lifting equipment chain. There is no dedicated AS/NZS standard specific to eye bolts — DIN 580 and BS 4278 are the benchmarks used by Australian lifting equipment suppliers and accepted by regulators under the WHS framework.

2. Types of Eye Bolts: A Complete Overview

The term "eye bolt" covers a wide family of fasteners. Not all of them are rated for lifting, and those that are rated carry very different capacities depending on type and load direction. Here is the complete taxonomy.

Plain (Uncollared) Eye Bolt — DIN 580

The plain eye bolt has no collar or shoulder. The eye is formed at the top of the shank and the underside of the eye bears directly against the parent material surface. Plain eye bolts are rated for vertical (0°) lifts only. Any deviation from vertical introduces a bending moment at the shank-to-eye junction that rapidly exceeds the design capacity. DIN 580 plain eye bolts are forged from carbon steel and carry a stamped WLL for vertical use. They are the most common type found in Australian workshops and the most commonly misused.

Collared (Shouldered) Eye Bolt — BS 4278

The collared eye bolt has a machined shoulder flange beneath the eye. When the bolt is fully threaded into the parent material, this collar bears flush against the surface and distributes the angular force component across a much larger contact area. This load distribution is what gives a collared eye bolt its angular capacity. BS 4278 defines the exact geometry, forging requirements, proof load testing, and WLL values for collared eye bolts at vertical and at specified angles (0°, 15°, 30°, 45°). Beyond 45° from vertical, even a correctly installed BS 4278 collared eye bolt must not be loaded.

Critically: the collar must be fully and flush seated against the parent material face. If the thread depth is insufficient and the collar is suspended above the surface — even by a few millimetres — the angular load capacity is effectively zero. This is covered in detail under Installation.

Swivel Eye Bolt

A swivel eye bolt has a bearing or swivel mechanism at the junction between the shank and the eye, allowing the eye to rotate freely around the shank axis. This prevents the eye from being loaded out of plane when a sling or hook shifts position. However, a standard swivel eye bolt does not provide angular load capacity in the same way a hoist ring does — it is still subject to capacity reduction at angles, depending on design. Always check the manufacturer's rating documentation for a swivel eye bolt before assuming full WLL at angle.

Swivel Hoist Ring

A swivel hoist ring (also called a pivoting eye bolt or articulating hoist ring) is a superior engineering solution for angular and multi-axis loads. Unlike a swivel eye bolt that rotates around one axis only, a hoist ring provides 360° of swivel plus 180° of pivot in the perpendicular plane. This two-axis freedom means the eye always self-aligns to the direction of pull, eliminating out-of-plane bending entirely. Hoist rings carry their full rated WLL at any angle. They are more expensive than collared eye bolts but are the correct specification for precision lifts, CNC machine tools, and any application where the load direction cannot be guaranteed vertical. Brands include Crosby, RUD, TE-CO, and Jergens.

Machinery Eye Bolt

Machinery eye bolts are heavy-duty, fully forged eye bolts designed for permanent installation in the lifting bosses of industrial machinery — motors, gearboxes, compressors, press platens. They are typically high-proof-tested, individually serialised, and supplied with test certificates. WLL values are higher per thread size than standard DIN 580 eye bolts due to superior forging and material grade.

Weld-On Eye Bolt (Pad Eye)

Weld-on eye bolts — commonly called pad eyes — are welded directly to a structural member or frame to provide a permanent lift or restraint point. The base plate is welded to the parent structure; the eye bolt or eye plate extends above. Weld-on pad eyes eliminate the thread engagement issue but require qualified structural welding and weld inspection to be safe for lifting service. The weld quality and parent material properties govern the WLL.

Screw Eye (Ring Screw) — NOT FOR LIFTING

Screw eyes are commonly stocked in the same bin as legitimate eye bolts at hardware stores. The distinction is: a screw eye has a wood-screw thread point (tapered, coarse), is not stamped with a WLL, and has no shoulder or collar. A lifting eye bolt has a metric or BSW machine thread, is forged and proof-tested, and is stamped with a WLL and standard reference.

3. DIN 580 vs BS 4278: Understanding the Standards

When purchasing eye bolts for lifting in Australia, you will encounter products referencing DIN 580 and BS 4278. Understanding what each standard actually requires is essential — and understanding what the absence of a standard marking means is equally important.

DIN 580 — Plain Forged Eye Bolts

DIN 580 is a German standard (Deutsches Institut für Normung) that specifies the geometry, material, mechanical properties, surface treatment, and testing requirements for forged lifting eye bolts without a collar. Key requirements of DIN 580 include:

• Forged construction: Eye bolts must be drop-forged, not cast or fabricated from wire or bar stock. Forging aligns the grain structure of the steel with the shape of the part, producing far greater ductility and fatigue resistance than casting.
• Material: Typically carbon steel, minimum tensile strength specified. Stainless steel versions exist but carry lower WLL for the same thread size.
• Proof load testing: Each lot is proof load tested to 2× WLL minimum before release.
• Marking: Must be permanently marked with thread size, WLL (in tonnes), and the DIN 580 designation.
• Vertical use only: The standard explicitly rates the eye bolt for 0° (vertical) load only. No angular capacity is defined in DIN 580.

BS 4278 — Collared Eye Bolts

BS 4278 is the British Standard for eyebolts for lifting purposes. It is the primary standard for collared (shouldered) eye bolts used in lifting service and is the benchmark used by most reputable Australian lifting equipment suppliers. Key requirements include:

• Collar (shoulder): Mandatory. Geometry is specified — the collar must be of sufficient diameter and thickness to distribute angular loads safely.
• Forged construction: Required. Same grain-structure and ductility argument as DIN 580.
• Angular capacity: Defined in the standard. WLL is specified at 0° (vertical) and at 15°, 30°, and 45° from vertical. The capacity decreases significantly with angle (see tables below).
• Proof load testing: Higher proof load requirements than DIN 580, reflecting the greater demands of angular service.
• Marking: Thread size, WLL at vertical, and BS 4278 designation. Some manufacturers also mark the angular WLL values.

Comparison Summary

What About Products With No Standard Reference?

Eye bolts that are not marked with DIN 580, BS 4278, or an equivalent nationally recognised standard are not certified lifting components. They may be sold under a product description that includes "eye bolt" or "lifting ring" without meeting the forging, proof testing, or marking requirements of any standard. These products must not be used in lifting service. If you cannot verify the standard a product is manufactured to, treat it as non-rated hardware.

When purchasing from AIMS, all lifting-rated eye bolts are supplied with certification to the applicable standard. Uncertified products are sold into non-lifting applications only.

4. WLL and Load Rating Tables (M6–M30)

Working Load Limit (WLL) — previously called Safe Working Load or SWL — is the maximum mass the eye bolt is rated to carry in normal service. WLL values are calculated from the Minimum Breaking Load (MBL) divided by the design factor of safety, which for most lifting eye bolts is 4:1 or higher.

Important: The WLL values in the tables below are representative values based on DIN 580 and BS 4278 standards. Actual WLL varies by manufacturer and material grade. Always use the WLL stamped on the specific fastener and the manufacturer's load data, not generic table values, for actual lift planning.

DIN 580 Plain Eye Bolt — Vertical WLL

DIN 580 vertical WLL values only. Do not apply these ratings at any angle.

BS 4278 Collared Eye Bolt — WLL at Vertical and Angular Loads

The following table shows representative WLL values for BS 4278 collared eye bolts. Note how dramatically the capacity falls as the angle from vertical increases. The angle column refers to the angle between the lifting sling (or the direction of pull) and the vertical axis through the eye bolt shank.

BS 4278 representative values. Collar must be fully seated. Always verify WLL against manufacturer documentation and the marking on the eye bolt itself.

The De-Rating Factors at a Glance

To use this table: find the maximum angle your sling or chain will make with the vertical axis of the eye bolt shank. Apply the corresponding factor to the vertical WLL. That result is the maximum load you may apply in service.

Example: You have M20 collared eye bolts with a vertical WLL of 1.6 t. Your two-leg sling runs from the eye bolt to the load at 30° from vertical (60° included angle between sling legs). Your usable WLL per eye bolt is 1.6 t × 0.40 = 0.64 t (640 kg). For a two-point lift with two such eye bolts, total usable WLL = 1.28 t — not the 3.2 t you would calculate from two eye bolts at full vertical rating.

5. Angle Loading: The Rule That Gets People Killed

Angle loading is the most dangerous and most commonly misunderstood aspect of eye bolt selection. Accidents involving eye bolt failure almost always involve angular loading — either a plain eye bolt loaded at an angle, or a collared eye bolt loaded beyond its angular de-rating without the rigger accounting for the reduced capacity.

Why Angle Loading Is So Destructive

When a load is pulled at an angle to the shank axis, the force resolves into two components: an axial (tensile) component pulling along the shank, and a transverse (bending) component trying to bend the shank sideways at the surface of the parent material. For a plain eye bolt, which has no collar to distribute the transverse component, this bending stress concentrates at the shank-eye junction — exactly the weakest point in the forging. The part does not gradually deform; it can fracture without warning.

For a collared eye bolt, the collar distributes the transverse force component over a larger contact area on the parent material surface, reducing the bending stress. But even with a collar, the geometry has limits — hence the 45° maximum and the progressive de-rating across the 0°–45° range.

Common Scenarios That Create Angular Loading

• Multi-leg slings: A two-leg or four-leg sling always loads the eye bolt at an angle unless the sling legs are perfectly vertical. A sling with 60° included angle (30° per leg from vertical) applies 40% of vertical WLL capacity to each eye bolt.
• Loads shifted during the lift: Even if the initial load direction is vertical, any shift — from wind, from the load swinging, from picking up a load that is not directly below the hook — introduces angular loading mid-lift.
• Horizontal pulls: Using an eye bolt as a sideways anchor point for chain blocks or come-alongs creates extreme angular loading (close to 90°) that is categorically unsafe with any standard eye bolt.
• Offset load COG: If the load's centre of gravity is not directly below the rigging attachment point, the sling angle increases and the eye bolt sees angular loading even when the crane hook appears to be directly above.

Recognising Angular Loading in the Field

Check the angle of your sling legs or chain before the lift, not after. An included angle of 90° between two sling legs means each leg is at 45° from vertical — the absolute limit for collared eye bolts and well past the limit for plain eye bolts. An included angle of 120° (not uncommon with short slings on wide loads) means each leg is at 60° — completely prohibited territory for any standard eye bolt. Use longer slings to reduce the included angle or use hoist rings.

A simple field check: if the sling leg is closer to horizontal than to vertical, the angular loading has exceeded 45° from vertical. That lift must stop, be re-rigged, or use hoist rings.

6. Correct Orientation: The In-Plane Rule

The in-plane rule is the second most frequently violated eye bolt requirement, and like angular loading, it causes failures that appear sudden and without warning.

What Is the In-Plane Rule?

An eye bolt must be oriented so that the plane of the eye (the flat face of the ring) is aligned with the direction of pull. In other words, the sling, hook, or shackle passing through the eye must pull in the same plane as the ring lies — not sideways across it.

When a force is applied sideways to the eye (across the plane of the ring rather than along it), the ring is subjected to a twisting/bending load that it is not designed to resist. This out-of-plane loading can collapse the ring laterally, bend the shank at the surface junction, or cause the shackle or hook to cam out of the eye unpredictably.

How This Fails in Practice

The most common cause of out-of-plane loading is using a multi-leg sling where each sling leg pulls in a different direction. If two sling legs pass through one eye, but pull in different directions, the eye is being loaded out of plane by one of them. The fix: use a shackle through the eye and attach the sling legs to the shackle, so the shackle bow aligns with the sling legs.

For overhead lifts where the direction of pull rotates as the crane travels, a swivel hoist ring will self-align continuously to maintain in-plane loading regardless of the crane's position. For fixed-direction pulls where you control the geometry, ensure the eye is oriented to match the pull direction before you begin and lock it in that position if possible.

Swivel Eye Bolts and the In-Plane Problem

A swivel eye bolt addresses the in-plane issue for loads that rotate around the shank axis — the eye can rotate to follow the direction of pull in the horizontal plane. However, a basic swivel eye bolt still relies on the rigging geometry keeping the load in a consistent vertical plane. It does not provide the two-axis freedom of a hoist ring. For complex lifts where the load direction may shift in three dimensions, a hoist ring is the correct solution.

7. Collared vs Plain Eye Bolts: Which Do You Need?

The decision between a collared and a plain eye bolt is not a matter of preference — it is driven by whether angular loading is possible in your application.

Use a Plain (DIN 580) Eye Bolt When:

• The lift is strictly vertical with a single, directly overhead attachment point
• The sling geometry guarantees 0° from vertical throughout the lift
• The load will not shift, swing, or rotate during the lift
• The application is a fixed, single-direction anchor point where the load direction is permanently vertical

In practice, "strictly vertical" is harder to guarantee in the field than it sounds. Any time there is doubt, use a collared eye bolt. The WLL difference between plain and collared in vertical use is not significant; the safety margin from the collar when a load unexpectedly shifts is enormous.

Use a Collared (BS 4278) Eye Bolt When:

• Any multi-leg sling arrangement will be used (always creates angular loading)
• The load may shift or swing during the lift
• The eye bolt is used as a permanent rigging point where the crane approach direction varies
• The lift plan specifies angular loading at 15°, 30°, or 45°
• As a general-purpose lifting point where load direction cannot be guaranteed

Use a Swivel Hoist Ring When:

• Load direction will change during the lift or varies between lifts
• Loads exceed 45° from vertical at any point in the lift
• Precision lifting of CNC machines, tooling, or equipment where exact control of load path is required
• Permanent lifting points on equipment that travels in overhead crane service

8. Swivel Eye Bolts vs Swivel Hoist Rings

Both swivel eye bolts and swivel hoist rings allow some degree of self-alignment, but they differ fundamentally in how many axes of freedom they provide and how that affects the WLL at angle.

Swivel Eye Bolt

A swivel eye bolt has the eye assembled on a bearing that allows rotation around the shank axis (think of spinning the ring like a propeller). This one degree of freedom means the eye can follow a load that rotates horizontally — for example, as a crane travels sideways with a suspended load. It does not, however, provide any self-alignment in the vertical plane. If the load pulls the eye bolt at 30° from vertical, the geometry is the same as for a collared eye bolt at 30° — the de-rating applies and the collar must be seated.

Swivel eye bolts are useful in permanent crane service installations where the crane approach direction changes from lift to lift, because the eye will naturally orient to the in-plane direction without the rigger needing to manually orient the bolt. But they still require the same angular load calculations as a standard collared eye bolt.

Swivel Hoist Ring

A swivel hoist ring provides two independent axes of movement:

• 360° swivel: The ring rotates around the shank axis (same as a swivel eye bolt)
• 180° pivot: The ring can also tip in the perpendicular plane — toward or away from the mounting surface — following the actual direction of the sling leg regardless of whether it is vertical, horizontal, or any angle between

Because the ring always aligns with the direction of pull in both planes simultaneously, the load path through the ring and into the shank is always axial — there is no bending moment, no out-of-plane loading, and no angular de-rating. The full WLL applies regardless of load direction. This is the critical engineering advantage of a hoist ring over any fixed or single-axis-swivel eye bolt.

Hoist rings are precision components — they cost 3–5× more than a collared eye bolt of equivalent thread size. But for permanent lifting points on high-value machinery or in high-cycle crane service, they pay for themselves quickly in reduced rigging complexity and eliminated angle-loading risk.

9. Eye Bolt Materials: Carbon Steel vs Stainless

Lifting eye bolts are manufactured in carbon steel (typically zinc-plated or hot-dip galvanised) and stainless steel (304 or 316 grade). The choice of material affects corrosion resistance, WLL, and cost.

Carbon Steel Eye Bolts

Carbon steel is the default for most industrial lifting applications. Forged from medium-carbon or alloy steel, these eye bolts offer the highest WLL for a given thread size. Zinc electroplating provides modest corrosion protection suitable for dry indoor environments. Hot-dip galvanising provides substantially better protection and is appropriate for outdoor, humid, or mild-chemical environments.

Carbon steel eye bolts are not suitable for marine environments, food-processing areas, or any environment where chloride contamination is present. Salt and chlorides cause rapid pitting corrosion that is invisible inside the shank thread and can drastically reduce actual tensile strength without any visible external indication.

Stainless Steel Eye Bolts (Grade 304 and 316)

Stainless steel eye bolts are specified for corrosive environments — marine installations, coastal workshops, food processing, chemical handling, pharmaceutical facilities, and outdoor lifting points exposed to the elements. Grade 304 (A2 stainless) provides good general corrosion resistance. Grade 316 (A4 stainless) adds molybdenum for superior chloride and saltwater resistance — the correct choice for marine applications and food-grade environments.

Important caveats for stainless steel lifting eye bolts:

• Lower WLL than carbon steel: Stainless steel eye bolts typically carry a WLL approximately 20–30% lower than an equivalent carbon steel eye bolt of the same thread size. Check the marking on the specific fastener — do not assume carbon steel WLL values apply to stainless.
• Galling risk: Stainless-to-stainless thread engagement is prone to galling (thread seizure due to adhesive wear). Apply anti-seize compound (nickel-based, food-grade if required) to the threads before installation. This does not affect WLL if applied correctly.
• Must still be forged: Stainless steel eye bolts must still be forged, not cast. A cast stainless eye bolt is no safer than a cast carbon steel eye bolt — the failure mode (brittle fracture without warning) is the same regardless of material.

Forged vs Cast — A Critical Safety Distinction

This point is important enough to stand alone. Forged eye bolts and cast eye bolts are fundamentally different safety propositions, and it is not always easy to tell them apart visually in a mixed bin or catalogue listing.

Forged eye bolts: Manufactured by pressing hot steel into a die. The forging process aligns the grain structure of the steel to follow the shape of the part. This gives the eye bolt ductility — if overloaded, it will deform (stretch, neck, or bend) before it fractures. Deformation is visible and gives warning that failure is approaching.

Cast eye bolts: Manufactured by pouring molten metal into a mould. The grain structure is random and often contains shrinkage voids, porosity, and inclusions. Cast eye bolts fail suddenly in a brittle fracture — there is no deformation before the break. A cast eye bolt can carry its nominal load for months and then fail catastrophically on an ordinary lift with no warning.

How to identify: Forged eye bolts show a parting line (a fine seam running around the circumference where the die halves met) and have a smooth, dense surface. Cast eye bolts often show rougher surface texture, may have visible witness marks from the mould, and typically feel lighter for the same size. When in doubt, buy from a verified supplier and demand a certificate of conformity to DIN 580 or BS 4278 — both standards mandate forged construction.

10. How to Install an Eye Bolt Correctly

Correct installation is as important as correct selection. A properly specified eye bolt installed incorrectly is just as dangerous as using the wrong type altogether. Follow these steps every time.

Step-by-Step Installation Procedure

1. Verify the eye bolt is correct for the application. Check thread size, WLL, standard (DIN 580 or BS 4278), and material. Confirm the WLL exceeds the design load including all de-rating for angle. Confirm the eye bolt is forged and marked.
2. Prepare the tapped hole. The hole must be correctly tapped (not undersized or oversized). Clean the thread of swarf, debris, and any contamination. For stainless steel eye bolts, apply anti-seize to the external thread before installation.
3. Thread engagement — critical minimum. The shank must be engaged for a minimum of 1.5× the thread diameter in steel parent material. For M20 eye bolt: minimum 30 mm engagement. For softer parent materials (aluminium, cast iron), increase engagement to 2× diameter minimum. More engagement is always better — use a longer shank or through-bolt if the parent material permits.
4. Thread the eye bolt by hand until snug. Do not use power tools to drive eye bolts — the risk of cross-threading and of snagging the ring on adjacent structure is high.
5. Orient the eye correctly. For a planned lift direction, rotate the eye bolt so the plane of the eye aligns with the pull direction. For a collared eye bolt, the collar must be flush with the parent material surface at this orientation point.
6. The paper test — collar seating. With the eye bolt at the correct orientation and fully tightened, try to slide a sheet of paper between the collar and the parent material surface. If the paper slides under the collar at any point, the collar is not seated flush. A non-seated collar negates the angular load rating of the eye bolt. Do not continue the lift. Either re-tap the hole deeper, use a longer shank, or use a spacer washer if the manufacturer's data specifically permits this (most do not for angular lifts).
7. Do not shim the collar with washers. Placing washers under the collar to achieve flush seating is not acceptable for angular loads. The collar must contact the parent material directly and uniformly.
8. Tighten to the correct torque. Use the manufacturer's torque specification. Over-torquing can pre-stress the shank and reduce its effective load capacity; under-torquing can allow the eye bolt to rotate or unscrew under dynamic loading.
9. Inspect before use. Visually inspect the installed eye bolt: no cracks, correct orientation, collar flush, no visible deformation of the eye.
10. Attach rigging in-plane. Pass the sling or shackle through the eye so the load will be applied in the plane of the eye, not across it. If using a shackle, ensure the bow is properly oriented.

Through-Bolt Installation

When the parent material is too thin for adequate thread engagement, or when a through-bolt installation is specified, pass the shank through a clearance hole and apply a standard nut (and washer if appropriate) on the back face. Tighten the nut to the manufacturer's torque specification. Through-bolt installations can achieve higher WLL than tapped installations because thread engagement is no longer a limiting factor. Ensure the nut is locked (Nyloc, tab washer, or safety wire) to prevent rotation or backing off under vibration.

11. Inspection and Rejection Criteria

Eye bolts in lifting service must be inspected before every use and periodically (at least annually, or as required by the lift plan, manufacturer, and local WHS requirements). Remove any eye bolt from service that exhibits any of the following.

Visual Rejection Criteria

• Cracks or fractures: Any visible crack anywhere in the eye bolt, including at the base of the eye, around the collar, or in the shank. Zero tolerance.
• Deformed eye: The ring has changed shape — stretched, bent sideways, or collapsed. This indicates overloading. Remove from service even if the deformation appears minor.
• Bent shank: Any bending of the shank from its original straight form. Indicates past angular overloading.
• Neck elongation: The junction between the shank and the eye has stretched. Measure against a reference dimension or compare against a new eye bolt of the same size. Rejection threshold is typically 5% elongation from original dimensions.
• Collar damage: Chipped, worn, cracked, or missing collar on a BS 4278 eye bolt. If the collar is damaged, the angular load rating is compromised.
• Thread damage: Cross-threading, stripped threads, or significant corrosion on the thread. Damaged threads reduce the effective thread engagement and the WLL of the installed eye bolt.
• Deep corrosion or pitting: Surface rust that can be cleaned off does not necessarily require rejection, but deep pitting — particularly on the shank, at the shank-eye junction, or under the collar — does. Internal corrosion in the thread engagement zone is not visible; if in doubt, replace.
• Illegible markings: If the WLL, thread size, or standard designation cannot be read, the eye bolt cannot be assigned a WLL and must not be used for lifting. Do not assume the WLL from size alone.
• No WLL marking: If the eye bolt was never marked — it is a screw eye, a piece of hardware, or an uncertified item. Remove from the lifting equipment inventory immediately.

Periodic Inspection

Under AS 4991 and the WHS Regulations, lifting components must be maintained and inspected in accordance with the manufacturer's recommendations and at intervals appropriate to the duty cycle. For eye bolts in regular lifting service, an annual documented inspection by a competent person is the minimum. For high-cycle applications (multiple lifts per day), quarterly inspection may be required. Keep records of every inspection — date, inspector, condition, and any action taken.

12. Common Mistakes (and Why They Are Dangerous)

13. Selection Guide by Application

Use this table as a starting point. All selections assume correctly installed, certified eye bolts. Verify WLL against actual loads including de-rating before any lift.

14. AIMS Eye Bolt Range

AIMS stocks a range of certified lifting eye bolts and related hardware for Australian industry. Our range includes:

• Austlift certified lifting eye bolts — DIN 580 plain and BS 4278 collared, forged carbon steel, individually WLL-marked, with conformity documentation. Available in M6 through M36. Austlift is a leading Australian lifting hardware brand supplying to industry, mining, and construction.
• Stainless steel lifting eye bolts (Grade 316) — BS 4278 collared in 316 stainless, for marine, food, and corrosive-environment applications. Hobson Engineering supply stainless hardware with full material certification.
• Eye nuts — For through-bolt applications where the eye nut is applied from the back face and a standard bolt is used on the load side. Matched WLL to equivalent eye bolt sizes.
• Swivel eye bolts — Single-axis swivel for permanent crane service points where the approach direction varies.

All eye bolts sold by AIMS for lifting applications come with WLL markings and are sourced from manufacturers who comply with DIN 580 or BS 4278. We do not stock uncertified or cast eye bolts in our lifting hardware range.

If you need assistance specifying the correct eye bolt for a particular lifting scenario — thread size, WLL calculation, angular de-rating, or material selection for a corrosive environment — contact our team. We work with maintenance engineers, riggers, and procurement teams across Australian industry daily.

Browse the AIMS eye bolt and eye nut range — or call us to discuss your specific application.

For related rigging hardware, see our guides on bow shackles and D-shackles, snatch blocks, electric hoists, and chain blocks.

Chain slings are commonly paired with lifting eye bolts in multi-leg lifting assemblies. For G80 and G100 chain sling grades, WLL tables, sling angle de-rating, and AS 3775 inspection requirements, see the Chain Sling Guide.

15. Frequently Asked Questions

What is an eye bolt and what is it used for?

An eye bolt is a threaded fastener with a closed circular loop (eye or ring) at one end. It screws into a tapped hole or through a clearance hole in a load, structure, or machine component, providing a permanent or temporary attachment point for hooks, shackles, wire rope slings, chain slings, and other rigging hardware. Eye bolts are used for lifting and hoisting machinery, installing permanent crane anchor points, suspending equipment overhead, and restraining loads during transport. Not all products called eye bolts are rated for lifting — only forged, certified eye bolts with a stamped WLL (Working Load Limit) are suitable for overhead lifting service.

What is the difference between a plain (uncollared) and collared eye bolt?

A plain (uncollared) eye bolt has no shoulder flange beneath the eye — the underside of the eye bears directly on the parent material surface. It is rated for vertical (0°) lifts only and must never be loaded at an angle. A collared (shouldered) eye bolt has a machined flange (collar) that bears against the parent material surface. The collar distributes angular force components over a larger area, giving the eye bolt defined angular load capacity. Under BS 4278, collared eye bolts are rated at reduced WLL from 0° to 45° from vertical, with the capacity at 45° being 25% of the vertical WLL. Beyond 45°, even a collared eye bolt must not be loaded.

How much weight can an eye bolt hold?

This depends entirely on the eye bolt type, thread size, installation quality, and load angle. As a guide for DIN 580 plain eye bolts (vertical use only): M12 = 0.32 t, M16 = 0.63 t, M20 = 1.0 t, M24 = 1.6 t, M30 = 2.7 t. For collared BS 4278 eye bolts at vertical: M12 = 0.5 t, M16 = 1.0 t, M20 = 1.6 t, M24 = 2.5 t, M30 = 4.0 t. These values assume correct installation with adequate thread engagement and a flush collar seating (where applicable). Always use the WLL stamped on the specific eye bolt — not generic table values — and apply de-rating if the load direction is not perfectly vertical.

How do I calculate WLL for an angled lift using a collared eye bolt?

Multiply the vertical WLL of the eye bolt by the de-rating factor for your lift angle. The de-rating factors for BS 4278 collared eye bolts are: 0° (vertical) = ×1.00; up to 15° = ×0.63; up to 30° = ×0.40; up to 45° = ×0.25; above 45° = do not use. Example: M20 collared eye bolt, vertical WLL 1.6 t, lifting at 30° from vertical. Usable WLL = 1.6 × 0.40 = 0.64 t (640 kg). The load being lifted must not exceed 640 kg for that eye bolt in that configuration. If using two eye bolts in a multi-leg sling, calculate the angle for each leg separately and apply the de-rating to each eye bolt independently.

What is the angle de-rating rule for eye bolts?

The angle de-rating rule applies to collared (BS 4278) eye bolts only. As the angle from vertical increases, the WLL decreases: vertical (0°) = 100% of rated WLL; up to 15° = 63%; up to 30° = 40%; up to 45° = 25%; above 45° = prohibited, do not use under any circumstances. This rule exists because angular loading introduces a transverse (bending) force component at the eye-shank junction. The collar distributes this component, but only up to 45°. Plain (uncollared) DIN 580 eye bolts have no angular capacity at all — any deviation from vertical is prohibited.

Can I use a plain eye bolt for an angled lift?

No. A plain (uncollared) DIN 580 eye bolt must not be used for any lift involving angular loading. Plain eye bolts have no collar to distribute the transverse force component created by angular loading. The bending stress concentrates at the shank-eye junction and can cause sudden fracture without visible warning, even at loads well below the stamped vertical WLL. If your lift involves any deviation from perfectly vertical — including from multi-leg slings, load swing, or shifting centre of gravity — you must use a collared BS 4278 eye bolt (at maximum 45° from vertical) or a swivel hoist ring.

What does DIN 580 mean on an eye bolt?

DIN 580 is a German standard (Deutsches Institut für Normung, standard 580) specifying the geometry, material, manufacturing process (forged), proof load testing, and marking requirements for plain lifting eye bolts without a collar. When you see DIN 580 stamped on an eye bolt, it means the fastener has been manufactured to that standard — it is forged (not cast), has been proof tested to at least twice the WLL, and the WLL stamped on it is a certified value. DIN 580 eye bolts are rated for vertical lifts only. The DIN 580 standard is widely accepted in Australia as the benchmark for plain lifting eye bolts in the absence of a dedicated AS/NZS standard.

What is the difference between DIN 580 and BS 4278?

DIN 580 covers plain (uncollared) forged lifting eye bolts rated for vertical loads only. BS 4278 covers collared (shouldered) forged lifting eye bolts that have defined angular load capacity from 0° to 45° from vertical, with WLL reducing progressively with angle. BS 4278 requires a specific collar geometry that must seat flush against the parent material to provide its angular rating. Both standards require forged construction and stamped WLL markings. If you need to lift at any angle, BS 4278 collared eye bolts are required — DIN 580 plain eye bolts are not suitable. Both standards are used in Australia; there is no dedicated Australian Standard specifically for eye bolts.

What is a swivel eye bolt and when should I use one instead of a standard eye bolt?

A swivel eye bolt has a bearing mechanism at the junction between the shank and the eye ring, allowing the eye to rotate 360° around the shank axis. This allows the eye to self-align with the direction of horizontal pull, preventing out-of-plane loading when the load direction changes between lifts or as a crane travels. Use a swivel eye bolt when: the crane approach direction varies between lifts and you cannot predict the sling angle; when a permanently installed anchor point will be used from multiple directions; or when a fixed eye bolt would regularly be left at the wrong orientation and then manually adjusted (which risks incorrect orientation under load). Note: a swivel eye bolt still requires angular de-rating calculation — it provides horizontal rotation only, not full multi-axis freedom. If you need full angular capacity in all planes, use a swivel hoist ring.

What is the difference between a swivel eye bolt and a swivel hoist ring?

A swivel eye bolt rotates around the shank axis only (one axis of freedom — horizontal swivel). A swivel hoist ring provides 360° swivel around the shank axis plus 180° pivot in the perpendicular plane (two axes of freedom). Because a hoist ring can pivot in both planes, the eye always aligns with the actual direction of pull regardless of whether the load is vertical, horizontal, or at any angle between. This eliminates angular de-rating entirely — a hoist ring carries its full rated WLL at any angle of pull. Swivel hoist rings are larger, heavier, and 3–5× more expensive than equivalent eye bolts, but are the correct specification for precision lifts, high-cycle crane service, or any application where load direction changes in three dimensions.

How do I install an eye bolt correctly?

Follow these steps: 1) Verify the eye bolt is correct — right type, thread size, WLL, and standard. 2) Prepare the tapped hole — clean threads, apply anti-seize for stainless. 3) Achieve minimum thread engagement of 1.5× the thread diameter in steel (more in softer materials). 4) Thread by hand to snug — never use power tools. 5) Orient the eye in the plane of the intended pull direction. 6) Check collar seating — for collared eye bolts, use the paper test (if paper slides under the collar, it is not flush-seated and the angular rating does not apply). 7) Tighten to manufacturer's torque spec. 8) Inspect before attaching rigging. 9) Attach rigging in-plane with the eye orientation. Do not use washers under the collar, heat the eye bolt to adjust orientation, or assume the eye bolt is correctly installed without the paper test for angular lifts.

What is the 'in-plane' rule and why does it matter?

The in-plane rule states that the direction of pull on an eye bolt must lie in the same plane as the eye ring — not across it. When a sling or hook pulls the eye sideways (across the face of the ring rather than through it in the intended direction), the eye is subjected to out-of-plane bending loads that can collapse the ring laterally or cause the shackle or hook to disengage. The in-plane rule matters because out-of-plane loading can cause failure at loads far below the stamped WLL, with no visible warning. To ensure in-plane loading: orient the eye bolt so the plane of the ring aligns with the sling direction; use a shackle as an intermediate connector if multiple sling legs are used; or use a swivel hoist ring which self-aligns in all planes.

How deep should an eye bolt be threaded in?

The minimum thread engagement for an eye bolt in a steel parent material is 1.5 times the thread diameter (1.5d). For M20, that is a minimum of 30 mm; for M16, 24 mm; for M12, 18 mm. For softer parent materials such as aluminium or cast iron, increase to a minimum of 2× diameter (2d). For grey cast iron or other brittle materials, consult the manufacturer's data — some require 2.5d or a through-bolt. More engagement is always better. Insufficient thread engagement causes thread strip-out in the parent material at loads below the stamped WLL — the eye bolt itself may appear undamaged while the tapped hole fails. If the parent material is too thin for adequate engagement, use a through-bolt with a nut and washer on the back face.

What is the difference between a screw eye and a lifting eye bolt?

A screw eye (also called a ring screw or wood eye screw) is a hardware fastener for hanging pictures, routing cables, or domestic use. It has a wood-screw thread (tapered, coarse, designed to bite into timber), is made from mild steel wire bent into a ring and pointed shank, is not forged, carries no WLL, and has never been proof tested. It will deform or fracture suddenly under lifting loads with no warning. A lifting eye bolt has a metric or BSP machine thread (parallel, precision pitch), is forged from higher-grade steel, is proof tested to at least twice its WLL, has its WLL stamped on it, and conforms to a lifting standard (DIN 580 or BS 4278). If there is no WLL stamped on the fastener, it is not a lifting component. Never use a screw eye for overhead lifting under any circumstances.

Can I use stainless steel eye bolts for lifting?

Yes — if the eye bolt is forged, certified to DIN 580 or BS 4278, and has a WLL stamped on it. However, note that stainless steel eye bolts carry a WLL approximately 20–30% lower than an equivalent carbon steel eye bolt of the same thread size. Use the WLL stamped on the specific stainless eye bolt — do not apply carbon steel WLL values. Grade 316 stainless is the correct choice for marine and coastal environments, food processing, and anywhere chloride contamination is present. Grade 304 is suitable for general corrosive environments away from direct saltwater exposure. Apply anti-seize compound to stainless threads before installation to prevent galling (thread seizure). As with all lifting eye bolts, stainless steel models must be forged — cast stainless eye bolts fail in brittle fracture without warning and must not be used in lifting service.

For further guidance on lifting equipment selection, inspection, and rigging hardware, contact the AIMS Industrial team. We supply tradespeople, engineers, and maintenance teams across Australia with certified lifting components and hands-on product expertise.

View the AIMS eye bolt and eye nut range →

Cross-reference our Tap Types guide when picking between taper, plug, bottoming, gun and spiral flute taps.

Cross-reference our Metric Bolt Size Guide when working with metric M-series fasteners.