Grade 10.9
Bolts & Fasteners
Mumbai · India
What “Grade 10.9 Bolts & Fasteners” Actually Means
The two numbers in a property class marking under ISO 898-1 aren’t arbitrary — the first number, multiplied by 100, gives the minimum tensile strength in MPa, and the second number, divided by 10, gives the minimum yield-to-tensile ratio. For Grade 10.9, that works out to a minimum tensile strength of 1040 MPa and a yield strength that’s roughly 90% of that tensile figure — a genuinely high-strength fastener with comparatively little margin between the point it starts to yield and the point it actually breaks.
That property comes from a quenched and tempered heat treatment applied to medium-carbon or alloy steel — rapid quenching from an austenitizing temperature followed by a tempering cycle that trades some hardness for the toughness needed to avoid brittle failure. Getting that heat treatment consistent across a production batch is what actually separates a reliably performing 10.9 bolt from one that’s out of spec despite carrying the correct head marking.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and our Grade 10.9 fastener range is manufactured with controlled quench and temper cycles, verified by hardness and tensile testing under our ISO 9001:2015 quality system.
Where 10.9 Genuinely Earns Its Place
Meaningfully Stronger Than 8.8
Roughly 30% higher minimum tensile strength than Class 8.8, useful wherever the joint genuinely needs the extra capacity.
Lower Embrittlement Risk Than 12.9
Less sensitive to hydrogen embrittlement during plating than Class 12.9, making it a safer default for plated fasteners.
Widely Available Matching Hardware
Matching Class 10 nuts and hardened washers are broadly available, simplifying complete joint specification.
Verified Heat Treatment Every Batch
Hardness and tensile testing confirms correct quench and temper response rather than assuming the marking alone is enough.
Grade 10.9 Detailed Properties
Per ISO 898-1
- Min. Tensile Strength 1040 MPa
- Min. Yield Strength 940 MPa
- Yield-to-Tensile Ratio 0.90
- Min. Elongation 9%
- Hardness Range ~ 32–39 HRC
Typical Base Material
- Base Material Medium-carbon / alloy steel
- Heat Treatment Quenched & tempered
- Head Marking “10.9” forged on head
- Surface Finish Plain, zinc, or dacromet
- Testing MTC / NABL on request
Available Dimensions
- Metric Diameter M5 – M39
- Length Standard or custom to drawing
- Thread Type Metric coarse / fine
- Head Style Hex, socket cap, flange
- Matching Nut Class Class 10 (ISO 898-2)
Grade 10.9 vs 8.8 vs 12.9
Most metric high tensile enquiries eventually come down to choosing between these three classes. The comparison below is the one we walk through with buyers before quoting, so the class matches the actual load and plating requirement rather than habit.
| Property | Class 8.8 | Class 10.9 | Class 12.9 |
|---|---|---|---|
| Minimum Tensile Strength | 800 MPa | 1040 MPa | 1220 MPa |
| Minimum Yield Strength | 640 MPa | 940 MPa | 1100 MPa |
| Embrittlement Risk (if plated) | Low | Moderate | Higher — requires care |
| Typical Use Case | General structural/mechanical | Higher-load structural & automotive | Maximum-strength, controlled use |
| Relative Cost | Lower | Moderate | Higher |
Grade 10.9 Torque Values
Approximate dry (unlubricated) tightening torque for common metric sizes in Grade 10.9. Always confirm exact torque against your specific application, lubrication condition, and joint design before use.
| Size | Approx. Torque (Nm, dry) | Approx. Torque (Nm, lubricated) |
|---|---|---|
| M6 | ~12 | ~9 |
| M8 | ~29 | ~22 |
| M10 | ~57 | ~43 |
| M12 | ~99 | ~74 |
| M16 | ~245 | ~184 |
| M20 | ~478 | ~359 |
| M24 | ~826 | ~620 |
Torque figures are approximate reference values only, based on typical friction coefficients for Grade 10.9 fasteners. Actual required torque depends on the specific joint design, lubrication, surface finish, and target preload — always follow your engineering specification or torque-tension test results for critical applications.
Application Areas
Wherever the joint needs meaningfully more strength than 8.8 without 12.9’s handling sensitivity.
Structural Steelwork
structural connections
Automotive Drivetrain
and chassis bolting
Industrial Machinery
assembly and mounting
Wind Turbine Components
structural fastening
Construction Equipment
structural bolting
Rail & Transport Infrastructure
transport fastening
Pressure Vessel & Flange Bolting
joint applications
General Heavy-Duty Engineering
high-load mechanical assemblies
Standard Export Documentation
Prepared as standard practice for every Grade 10.9 fastener shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Hardness & Tensile Test Report
Batch-level testing confirming correct quench and temper response for Class 10.9.
Certificate of Conformance
Confirms the shipment matches the purchase order specification and grade in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
NABL Accredited Test Reports
Independent mechanical testing available on request for critical structural applications.
Bill of Lading
Ocean or air freight shipping document confirming carrier, mode, and consignee details.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
High Tensile Bolts Specifications
The full detailed specification breakdown for property class 8.8, 10.9, and 12.9 bolting.
View High Tensile Specs →High Tensile Bolt Grades Explained
A head-marking identification guide across metric and SAE grading systems.
View Grade Guide →High Tensile Fasteners for Pune
Fast regional supply of Class 8.8/10.9/12.9 fastening for Pune’s automotive manufacturing base.
View Pune Supply →Different Types of Nuts and Bolts
A guide to bolt head and nut designs across every standard fastening application.
View Nut & Bolt Types →Need More Strength
Without the Embrittlement Risk?
Tell us your load requirement and plating needs — we’ll confirm whether Grade 10.9 is the right fit for your application. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in