ISO 898

Covers — mechanical properties of carbon-steel and alloy-steel fasteners by property class: bolts, screws, and studs (Part 1) and nuts (Part 2), defining tensile strength, proof load, hardness, and (where applicable) impact and temperature limits.

Does NOT cover (exclusions) — the following are governed elsewhere:

• Stainless-steel fastener properties → ISO 3506.
• Fastener dimensions → ISO 4014 / 4017 / 4032.
• Imperial (inch) bolting materials → ASTM A193 / A307 / A320.

ISO 898 gives the strength (property class); ISO 4014/4032 give the size.

ISO 898 sets minimum requirements for fastener properties:

• Property Classes — e.g. 8.8, 10.9, 12.9, where the first number ×100 = tensile MPa/10 and the second encodes the yield ratio.
• Mechanical Properties — tensile, proof load, yield, hardness, and elongation per class.
• Nut Compatibility — Part 2 nut classes matched so the nut out-strengths the bolt.
• Marking — property-class marking on bolt heads and nuts.

ISO 898 is the metric fastener strength standard, defining property classes such as 8.8, 10.9, and 12.9 that encode tensile strength and yield ratio on the bolt head. Part 1 covers bolts, screws, and studs; Part 2 covers the matching nut classes.

It is the metric analog of the ASTM bolting material specs — but the callout is a property class, not a grade name, and the two systems must not be mixed. Dimensions come from ISO 4014/4017 (bolts) and ISO 4032 (nuts); stainless fasteners use ISO 3506.

Engineering Note: Read the head marking as a property class, not an imperial grade — an "8.8" bolt is a metric class with specific MPa properties, unrelated to any inch-series grade number.