Stainless Steel Lifting Eye Bolt

choosing the right eye bolt

What is an eye bolt & when to use it?

An eye bolt is a bolt with a threaded shank and an integral eye/ring at the head.
Use an eye bolt when you need:

A lifting or anchoring point on a structure, plate, or machine

To lift, guide, or secure equipment with hooks, shackles, chains, or ropes

A removable lifting point that screws into a tapped hole or through a plate with a nut

Typical applications:

Lifting and handling machinery, plates, fabrications, parts

Rigging and anchoring (guy wires, safety lines, fall-arrest anchors – where approved)

Temporary lifting points on skids, frames, and equipment during installation

For lifting, always use rated lifting eye bolts (e.g. DIN 580) and follow the manufacturer’s load charts.

Environment & corrosion – A2 vs A4 stainless

Choose the material grade based on the environment:

A2 (304) stainless eye bolt

For indoor, general outdoor, and mildly corrosive environments

Machinery lifting points, plant areas, warehouses, general fabrication

A4 (316) stainless eye bolt

For marine, coastal, chemical, and chloride-rich environments

Jetties, seafront structures, ship decks, treatment plants, food & pharma wash-down areas

Always match material with the rest of the hardware where possible:

A2 eye bolt with A2 nuts/washers/studs

A4 eye bolt with A4 nuts/washers/studs

Standard & type – lifting vs non-lifting eye bolts

You must distinguish between rated lifting eye bolts and simple hardware eye bolts:

Lifting eye bolts (e.g., DIN 580)

Designed and tested for lifting applications

Supplied with a Working Load Limit (WLL) for each size

Must be installed and used according to load direction and manufacturer’s instructions

Non-lifting / hardware eye bolts

Used for anchoring, tie-down, guiding, fencing, architectural use

Not certified for overhead lifting

Only suitable for static or lightly loaded applications

Rule:

If people or heavy loads are involved in lifting or suspension, use DIN 580 or equivalent lifting eye bolts – not general hardware eye bolts.

Load direction – in-line vs angled loading

Rated lifting eye bolts are strongest in straight, in-line loading:

Straight pull (0°) – along the axis of the shank = maximum WLL.

Angled loading (e.g., 45°, 90°) – the allowable WLL reduces, sometimes significantly.

Always:

Check the WLL table for different angles

Avoid side/pull-over loading that can bend the shank or eye

Align the eye so that the load direction is correct (many designs require the eye plane to align with sling direction)

Shank type – through-bolt vs tapped-hole use

Eye bolts can be used in two main ways:

Through-bolt with nut

The eye bolt passes through a plate/structure

Secured with a nut (and washer) on the opposite side

Good when you can access both sides and want a very secure anchor

Screwed into a tapped hole

Threads into a tapped boss, block or plate

Very common on machines and engine blocks

Requires adequate thread engagement depth and base material strength

Thread engagement guideline (tapped holes):

Typically at least 1× bolt diameter in steel for basic designs (often more for lifting – follow manufacturer standards/project spec).

Mechanical Properties (Guide) – Stainless Eye Bolts (Lifting Type, e.g. DIN 580)

For lifting eye bolts, the key mechanical parameter is the Working Load Limit (WLL), which is derived from:

Material tensile strength

Cross-section of the eye and shank

Built-in safety factor (usually 4:1 or more)

A2 Stainless Eye Bolts (DIN 580 type)

Material: A2 (304) stainless steel

Typical use:

Lifting points on machinery in general industrial and outdoor environments

Provide a WLL per size (e.g. M8, M10, M12, etc.), specified by the manufacturer.

A4 Stainless Eye Bolts (DIN 580 type)

Material: A4 (316) stainless steel

Typical use:

Lifting points in marine, coastal, food/pharma, and chemical environments

Also supplied with WLL per size, similar to A2 but with better corrosion resistance.

Key mechanical notes:

WLL is not the same as ultimate strength.

Ultimate strength = WLL × safety factor (e.g., ~4x or more).

WLL is valid only if:

The eye bolt is installed correctly

The load direction is within allowed angles

The base material and threads are properly designed to support the load

For non-lifting eye bolts (hardware type):

There may be no WLL marking

Mechanical behaviour is then governed only by thread size/material, not certified for lifting – they should not be used as lifting points.