ISO 898-1 Fastener Property Classes | Specifications

Standard Overview

What Is ISO 898-1?

ISO 898-1 specifies mechanical and physical properties for carbon-steel and alloy-steel bolts, screws and studs with specified property classes.

ISO 898-1:2013 covers bolts, screws and studs with specified property classes and coarse or fine pitch metric threads. The current ISO page states that the 2013 edition was reviewed and confirmed in 2025 and remains current. citeturn0search0

Mechanical Properties

Property Classes

The standard defines mechanical and physical requirements used to classify carbon-steel and alloy-steel fasteners.

Examples: 4.6, 5.8, 8.8, 10.9, 12.9

Product Scope

Bolts, Screws & Studs

It applies to specified metric fasteners rather than defining the geometry of every individual product standard.

Thread range: Coarse M1.6–M39; fine M8×1–M39×3

Important: ISO 898-1 is a mechanical-property standard. It does not by itself specify the product head dimensions, corrosion resistance, weldability, fatigue resistance, shear resistance or torque/clamp-force performance. citeturn0search0

Property Classes

Understanding Metric Fastener Classes

The class marking provides a concise indication of the fastener's specified strength level. Always verify the exact standard and product requirements before substitution.

Common Carbon / Alloy Steel Classes

Class	Approx. Nominal Tensile Strength (MPa)	Typical Engineering Position	Common Use
4.6	400	General / lower strength	General-purpose assemblies
5.8	500	Medium strength	General machinery and fabrication
8.8	800	High strength	Industrial machinery and structural assemblies
10.9	1,000	Higher strength	Heavy-duty machinery and highly loaded joints
12.9	1,200	Very high strength	High-strength machine and tooling applications

Class notation: For a class such as 10.9, the first number is associated with a nominal tensile strength of 1,000 MPa, while the second number expresses the nominal ratio used for the specified yield/proof-strength relationship. Final acceptance must be based on the applicable ISO 898-1 requirements and test values.

Scope & Requirements

What ISO 898-1 Covers

The ISO scope is specific to carbon/alloy steel fasteners and their mechanical and physical properties at the stated test temperature range.

Scope Summary

Item	ISO 898-1:2013 Scope
Material	Carbon steel or alloy steel
Products	Bolts, screws and studs with specified property classes
Thread	Triangular ISO metric screw thread
Coarse Thread	M1.6 to M39
Fine Pitch Thread	M8×1 to M39×3
Diameter / Pitch	In accordance with ISO 261 and ISO 262
Thread Tolerances	In accordance with ISO 965-1, ISO 965-2 and ISO 965-4
Test Temperature	Ambient temperature range of 10 °C to 35 °C

Temperature note: Fasteners conforming to ISO 898-1 are evaluated at the specified ambient temperature range and may not retain the specified mechanical and physical properties at elevated or lower temperatures. citeturn0search0

Mechanical Properties

What to Check on a Material Certificate

Tensile Strength

Verify the specified tensile-strength requirement for the selected property class and fastener size.

Yield / Proof Stress

Confirm the applicable yield or proof-strength requirement specified for the property class and product.

Hardness

Hardness requirements form part of the mechanical-property verification for applicable property classes.

Elongation

Check elongation requirements where tensile testing and the applicable class require them.

Material Verification

For controlled projects, confirm material and heat-treatment information against the purchase specification and certificate.

Inspection Documents

For RFQs, state whether a test certificate, MTC, inspection report or other documentation is required.

Selection Guide

How to Specify an ISO 898-1 Fastener

Specification	Example	Why It Matters
Product Standard	ISO 4014 / ISO 4017 / ISO 4762 etc.	Defines the product geometry and dimensional requirements
Thread Size	M16	Defines nominal diameter and thread selection
Length	50 mm	Defines the required grip/engagement length
Property Class	8.8 / 10.9 / 12.9	Defines the required mechanical-property level
Material / Finish	Alloy steel, coating as specified	Important for corrosion, processing and project requirements
Certificate	EN 10204 3.1, if specified	Defines required material / inspection documentation

RFQ format: "Hex bolt ISO 4014, M16 × 50, property class 8.8, finish as specified, quantity ___, certificate required."

Related Standards

Complementary Fastener Standards

Standard	Description	Relationship to ISO 898-1
ISO 898-2	Mechanical properties of nuts	Complementary standard for nuts matched to metric fastener assemblies
ISO 898-5	Mechanical properties of set screws and similar threaded fasteners	Relevant where the fastener is outside ISO 898-1 scope
ISO 3506	Mechanical properties of corrosion-resistant stainless-steel fasteners	Relevant for stainless-steel fasteners rather than carbon/alloy steel classes
ISO 4014	Hexagon head bolts with shank	Product geometry standard; property class may be specified using ISO 898-1
ISO 4017	Hexagon head screws with full thread	Product geometry standard; property class may be specified using ISO 898-1
ISO 4762	Socket head cap screws	Product geometry standard commonly paired with ISO 898-1 property classes
ISO 965	ISO metric screw thread tolerances	Defines applicable thread tolerance system referenced by ISO 898-1

FAQ

Frequently Asked Questions

What is ISO 898-1?

ISO 898-1 specifies mechanical and physical properties of carbon-steel and alloy-steel bolts, screws and studs with specified property classes and metric coarse or fine pitch threads. citeturn0search0

Is ISO 898-1 a bolt dimension standard?

No. ISO 898-1 primarily specifies mechanical and physical properties. Product-specific standards such as ISO 4014, ISO 4017 or ISO 4762 define the relevant product geometry and dimensions.

What does 8.8 mean?

8.8 is a metric fastener property class. The notation is used to identify a specified mechanical-property level under the applicable standard; it should not be confused with an ASTM/SAE “Grade” designation.

Does ISO 898-1 cover stainless steel?

No. ISO 898-1 covers carbon-steel and alloy-steel bolts, screws and studs. Corrosion-resistant stainless-steel fasteners are covered by the ISO 3506 series. citeturn0search0

Does ISO 898-1 cover set screws?

No. The ISO page specifically states that ISO 898-1 is not applicable to set screws and similar threaded fasteners that are not under tensile stress; ISO 898-5 is the relevant reference for that category. citeturn0search0

Does ISO 898-1 specify corrosion resistance?

No. The standard does not specify corrosion-resistance requirements. Finish and corrosion protection should be specified separately according to the application and project requirements. citeturn0search0

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