BS EN ISO 898-1:2013 Screw Loads (Proof, Tensile, Tightening Torque)
Per-size screw loads for ISO metric threads M6-M36 at property classes 4.6/8.8/10.9/12.9: nominal tensile stress area, minimum ultimate tensile load Fm,min, proof load Fp, and the source's estimated tightening torque — the load-side companion to the stress/hardness property-class table.
Last updated: 2026-11
Specifications
The property-class table says what a class is; this collected page says what that means in kilonewtons for a specific thread size. Four ladders run across M6 to M36 in the standard coarse pitches: the nominal tensile stress area As,nom (20.1 mm2 at M6 up to 817 mm2 at M36), then for classes 4.6, 8.8, 10.9 and 12.9 the minimum ultimate tensile load (a 12.9 M12 must carry 103 kN before fracture; the same thread at 4.6 only 33.7 kN), the proof load Fp the joint is rated to sit at permanently (81.8 kN at 12.9 M12), and the source's estimated tightening torque — 142.8 N·m at 10.9 M12, 2999 N·m at 12.9 M36 — which it computes from the proof loads at assumed friction, not from the standard: read it as a sensible assembly-starting estimate, not an acceptance value, and use a torque-tension study for anything critical. The M22 column is a reminder that stress area is not linear in diameter: M22 at 2.5 pitch (303 mm2) sits between M20 and M24, and the fine-pitch variants are not tabulated here at all.
| Standard | BS EN ISO 898-1:2013 — mechanical properties of fasteners made of carbon steel and alloy steel, part 1: bolts, screws and studs with specified property classes (coarse thread, M6-M36) |
|---|---|
| Stress area As,nom | M6: 20.1 / M8: 36.6 / M10: 58.0 / M12: 84.3 / M14: 115 / M16: 157 / M20: 245 / M22: 303 / M24: 353 / M30: 561 / M36: 817 mm2 at pitches 1.0-4.0 mm |
| Min. ultimate tensile load Fm,min | Class 4.6: 8.04 kN (M6) to 327 kN (M36); 8.8: 16.1 to 678; 10.9: 20.9 to 850; 12.9: 24.5 to 997 kN |
| Proof load Fp | Class 4.6: 4.52 kN (M6) to 184 kN (M36); 8.8: 11.6 to 490; 10.9: 16.7 to 792; 12.9: 19.5 to 792/997 ladder — the permanent-joint rating |
| Estimated tightening torque (source) | 4.6: 4.6 N·m (M6) to 1126 N·m (M36); 8.8: 11.8 to 2999; 10.9: 17.0 to 4149; 12.9: 19.5 to 792 (M36) — source estimate at assumed friction, not an ISO requirement |
| Not tabulated | Fine-pitch threads, sizes above M36, shear loads, fatigue, nut-side loads (ISO 898-2), torque-tension coefficients (K factor) — per RFQ |
Materials
- These ladders are carbon/alloy steel property-class values only — stainless A2/A4 runs on the ISO 3506 equivalent classes and does not map 1:1. For torque-critical joints the estimated torque column is a starting point: friction conditions (lubricated vs as-received) move the achieved preload by tens of percent, so specify the lubrication state and verification method on the RFQ
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (BS EN ISO 898-1:2013 Screw Loads (Proof, Tensile, Tightening Torque)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Why is the proof load, not the tensile load, the number to size a joint against?
The proof load Fp is the load the fastener must carry permanently without permanent set — take a bolt to its proof load, unload it, and it must measure as it did before. The minimum ultimate tensile load Fm,min is where it finally breaks. A joint works at some fraction of Fp (the tightening step itself consumes most of it as preload), so the usable design envelope ends near the proof-load ladder, while the tensile ladder is reserve for overload and the tightening-estimate column is assembly tooling, not joint capacity. The collected tables keep the three apart per class and size — a 10.9 M16 is 130 kN proof, 163 kN minimum ultimate, and an estimated 227.3 N·m to tighten — and mixing any two of them in a specification is the classic procurement error.
How should the estimated tightening torque column be used — and trusted?
As an estimate, exactly as the source labels it. It back-computes a wrench torque from the proof-load ladder at assumed thread and bearing friction, which is why an 8.8 M12 reads 57.3 N·m while a 10.9 of the same size reads 142.8 N·m — the geometry is identical, only the target preload changes. Real achieved preload scatters widely with friction: the same torque on a lubricated versus dry thread can differ by a third or more, and large sizes (the ladder reaches 4149 N·m at 10.9 M36) are beyond accurate torque control anyway. Use the column for tool selection and sanity checks on non-critical joints; for verified preload, specify angle control, hydraulic tensioning, or a measured K-factor on the RFQ.
Related knowledge
- What Bolt Property Classes 8.8, 10.9 and 12.9 Encode — and When High Strength Stops Being the Right Choice
- Bolt Grade Selection: ISO 898-1 8.8/10.9/12.9 vs ASTM A307 and A325
- 8.8 vs 10.9 vs 12.9 Bolts: Strength, Hardness and Cost — What the Evidence Settles
- Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
- How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint
- Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
- Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support