Stainless Steel Anti Theft Bolt

Choosing the right anti-theft bolt (security bolt)

Function – when to use an anti-theft bolt

Use an anti-theft (security) bolt when you want to discourage or prevent unauthorized removal of a component, especially in:

Public areas – street lights, sign boards, guard rails, barriers, benches

Outdoor equipment – CCTV poles, solar structures, telecom towers, gates

High-value or high-risk parts – covers, access doors, grating, machinery guards

A security bolt works by using a special head or drive so that it cannot be removed with standard tools (spanner, normal Allen key, normal Torx).

Environment & corrosion – material selection

Choose material based on site conditions and match to the rest of your fasteners:

A2 (304) stainless security bolt

For indoor and general outdoor conditions

City infrastructure, poles, railings, signage, equipment guards

A4 (316) stainless security bolt

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

Ports, seafront railings, bridges, water treatment, poolside, chemical plants

Rule:

Use A2 where normal stainless is sufficient.

Use A4 where there is salt, sea air, harsh cleaning, or chemicals.

Match to A2/A4 nuts, washers and surrounding hardware wherever possible.

Head & drive type – level of security vs serviceability

Choose the head/drive depending on whether the joint must later be opened or not:

One-way / permanent security bolts

Examples: one-way slotted, special low-profile heads designed to tighten easily but cannot be gripped for removal.

Ideal when no routine maintenance is expected and you want maximum tamper resistance.

Removal usually needs drilling or destructive methods.

Keyed / special-drive security bolts (removable with special tool)

Examples: pin-Torx (Tamper-Torx), pin-hex (tamper Allen), multi-lobe, unique pattern drives.

Require a matching bit or key that is not commonly available.

Best where you want good security but still need controlled removal for maintenance.

Shear-type security bolts (less common than nuts but used in some systems)

Hex head or drive shears off at a set torque, leaving a smooth, tamper-resistant head.

Used where permanent installation and tight torque control are both required.

Selection thumb rule:

No maintenance / permanent fixing → One-way or shear-type bolt.

Needs controlled maintenance → Keyed / special-drive bolt + controlled access to bits/keys.

Access & tooling – practical considerations

Before choosing:

Who will install and service this joint?

Can you control who has the special bits/keys?

Do you have clearance for the required tool (Tamper-Torx bit, pin-hex key, etc.)?

Plan to:

Keep spare bits/keys in a secure, documented place.

Avoid using too many different drive patterns across one project – standardise on 1–2 security drives if possible.

Mechanical Properties (Guide) – Stainless Steel Anti-Theft Bolts

Anti-theft bolts use the same material and property classes as standard bolts (e.g., A2-70, A4-70, A4-80).
The special head gives the security function; the tensile strength is governed by the property class.

A2-70 Anti-theft bolts

Material: A2 (304) stainless steel

Property class: 70 (min. tensile strength ≈ 700 MPa, typical proof strength ≈ 450 MPa)

Use with: A2-70 nuts and washers.

Typical applications:

Street furniture, guard rails, access covers, indoor/outdoor equipment in normal environments.

A4-70 Anti-theft bolts

Material: A4 (316) stainless steel

Property class: 70

Use with: A4-70 nuts (or A4-80 where specifically designed).

Typical applications:

Marine/coastal structures, chemical plants, water treatment, poolside, high-corrosion outdoor installations.

A4-80 Anti-theft bolts (if used)

Higher strength stainless, min. tensile strength ≈ 800 MPa.

For higher load or critical stainless joints where both strength and corrosion resistance are required.

Key mechanical points:

The property class (70 / 80) defines the basic tensile & proof strength, same as on standard stainless bolts.

For a given diameter (e.g., M10 A4-70 security bolt), the load-carrying capacity is comparable to a standard M10 A4-70 bolt.

The joint capacity is governed by:

Bolt strength (property class & size)

Nut/anchor strength

Clamped material thickness & quality

Any additional locking (nylock, washer, adhesive)

The security drive does not increase mechanical load capacity; it only makes unapproved removal more difficult.