Property Class 10.9 Metric Bolts (ISO 898-1 / ASTM F568M)
The metric Grade 8: alloy steel quenched and tempered to 1040 MPa (150 ksi) tensile and 940 MPa yield, 33 to 39 HRC — equivalent to A354 BD and A490 in the inch system.
What Class 10.9 is.
Class 10.9 is the high-strength metric bolt: 1040 MPa tensile, 940 MPa yield and an 830 MPa proof load, at 33 to 39 HRC. ISO 898-1 and ASTM F568M require medium-carbon alloy steel for the full size range (carbon steel is permitted only in small sizes) with a fine-grain hardenability requirement and a 425 °C minimum temper. It corresponds to SAE Grade 8, A354 BD and A490 in inches, and 10.9.3 is the weathering-steel version.
We machine 10.9 bolts, screws and studs in M5 to M100 from certified 4140 and 4340 bar, have them heat treated to the specification, and supply them plain, zinc-flake coated, or zinc plated with a hydrogen relief bake, with Class 10 nuts.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon (medium-carbon alloy steel) | C | 0.20 | 0.55 |
| Carbon (medium-carbon steel, M5–M20) | C | 0.25 | 0.55 |
| Phosphorus (alloy steel) | P | — | 0.040 |
| Sulfur (alloy steel) | S | — | 0.045 |
| Alloying elements | — | required for the full size range | — |
Values per ASTM F568M Table 1 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Property class and size | Proof load (MPa) | Tensile strength, min (MPa) | Yield strength, min (MPa) | Elongation, min (%) | Hardness |
|---|---|---|---|---|---|
| 10.9 — M5 to M100 | 830 | 1040 | 940 | 9 | C33–C39 |
| 10.9.3 weathering — M16 to M36 | 830 | 1040 | 940 | 9 | C33–C39 |
Values per ASTM F568M Table 3 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Proof load and tensile loads by thread size are in Table 5 of the specification.
Specifications that apply.
How Class 10.9 ships from Houston.
- Hex and heavy hex bolts and cap screws
- Studs and threaded rod
- Nuts and washers to match
- Machined specials to drawing
Class 10.9 fasteners we make.
Every item is manufactured to your drawing or standard in Class 10.9, imperial or metric, with an EN 10204 3.1 certificate.
What is a Class 10.9 bolt?
10.9 means 1000 MPa nominal tensile with yield at 90 percent of it; the specified minimums are 1040 and 940 MPa. At 33 to 39 HRC the bolt is as hard as a Grade 8, and it carries the same cautions: alloy steel is required so that it hardens through, the temper must be high enough to keep toughness, and electroplating needs a hydrogen relief bake. Zinc-flake coating avoids the hydrogen question entirely and is the normal finish on 10.9 in wind, automotive and mobile-plant work.
Testing, certification and marking
- Tensile, proof load and hardness tested per lot to ASTM F606
- Grade mark 10.9 and manufacturer's identification on the head or one end
- Certificate of conformance or test report with heat number on request; EN 10204 3.1 available
- Coating thickness reported when plated or galvanized
SAE Grade 8 / ASTM A354 Grade BD Bolts (150 ksi)
The high-strength alloy bolt: quenched and tempered alloy steel at 150 ksi tensile and 130 ksi yield in all sizes to 4 in. — Grade 8 in SAE terms, A354 BD in ASTM terms.
ASTM F3125/F3125M Grade A490 · Type 1 and Type 3ASTM F3125 Grade A490 Structural Bolts (150 ksi)
The high-strength structural bolt: alloy steel, 150 to 173 ksi tensile, ½ to 1½ in., never hot-dip galvanized — with the twist-off F2280 and metric A490M variants in the same specification.
ISO 898-1 · ASTM F568M Class 8.8Property Class 8.8 Metric Bolts (ISO 898-1 / ASTM F568M)
The metric Grade 5: medium-carbon steel quenched and tempered to 830 MPa (120 ksi) tensile and 660 MPa yield — the general-purpose high-strength metric bolt, equivalent to A449 and A325.