2026-09-02 · 8 min
Property Class 8.8 vs 10.9 vs 12.9: A Procurement Guide
A sourcing guide to the nominal ISO 898-1 property-class convention, its boundaries, and the information to include in an RFQ.
Property class markings such as 8.8, 10.9 and 12.9 are frequently used in fastener RFQs. They are useful procurement language only when the part, material, applicable standard, surface treatment and verification requirements are stated alongside the marking.
This page is a sourcing and specification-understanding guide. It is not engineering design advice, a substitution approval, or a torque, preload or load-selection guide.
What ISO 898-1 covers
ISO 898-1 specifies mechanical and physical properties for bolts, screws and studs made from carbon steel or alloy steel within its defined scope. A property class is therefore not a universal label for every fastener material, product form or service condition.
Within the standard's scope, testing is conducted at 10–35 °C and the covered threads are coarse M1.6–M39 and fine M8 × 1–M39 × 3. These limits describe the standard's scope, not JINSIXI's supply range.
Low-head and countersunk geometries may not meet some tensile and torsional requirements in the standard. Confirm the applicable requirements against the specific part and standard before specifying or approving supply.
For a purchase specification, cite the applicable standard and the product details that determine whether it applies. Do not use the class marking alone to infer corrosion performance, torque, fatigue behaviour or shear performance.
How the nominal class convention is commonly read
| Property class | Nominal tensile-strength convention | Nominal yield-ratio convention | Procurement reading |
|---|---|---|---|
| 8.8 | 8 × 100 = 800 MPa nominal | 0.8 nominal ratio | State the standard, part form and verification required. |
| 10.9 | 10 × 100 = 1,000 MPa nominal | 0.9 nominal ratio | Do not treat the marking as a substitute approval. |
| 12.9 | 12 × 100 = 1,200 MPa nominal | 0.9 nominal ratio | Confirm the specified product and supply condition. |
Important boundaries before comparison
The class marking answers only part of a fastener specification. Keep these distinctions visible in the RFQ and technical review:
- Nuts are covered separately by ISO 898-2. Do not derive a nut requirement solely from the bolt or screw property class.
- If torque or clamp force must be assessed, ISO 16047 addresses torque/clamp-force testing; a property class is not a torque instruction.
- When electroplated coatings are specified, ISO 4042 is relevant. Coating processes can introduce hydrogen-embrittlement risk where applicable, so define the coating and required process controls with the supplier.
- Set screws are treated separately in ISO 898-5. Do not assume a bolt/screw property-class statement covers a set screw.
- Stainless-steel bolts, screws and studs are addressed separately in ISO 3506-1; do not use this carbon/alloy-steel class comparison as a stainless-steel equivalency claim.
- Corrosion, fatigue and shear requirements need their own applicable requirements and review; they are not determined by this simplified class decoding.
RFQ checklist for property-class fasteners
Provide the following information so a supplier can confirm what is being requested instead of guessing from a class number:
- 1Part type, drawing or standard designation, dimensions, thread and head/form details.
- 2Required material and property class, including the applicable standard and revision where your specification requires it.
- 3Nut specification stated separately when nuts are included, including the applicable ISO 898-2 requirement where relevant.
- 4Surface treatment, corrosion environment and any coating-process controls or documentation required.
- 5Inspection, test-certificate, traceability, marking and lot requirements.
- 6Any application-specific torque, clamp-force, fatigue, shear, stainless-steel or set-screw requirement for separate technical review—not as an inference from 8.8, 10.9 or 12.9.
Related sourcing resources
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