Quick Summary
A hex bolt is a six-sided head fastener used to join components in structural, automotive, and industrial assemblies. This guide covers every aspect — types, grades (4.6 to 10.9), sizes (M6–M64), coatings, DIN/ISO/IS standards, and torque values — to help engineers and buyers make the right specification decision.
In This Guide
A hex bolt (also called a hexagonal head bolt or hex head bolt) is a fastener with a six-sided (hexagonal) head and a threaded shank. The head is designed to be driven by a wrench or spanner, making it one of the most widely used fastener types in the world.
Hex bolts are used to join two or more components together — typically by pairing with a nut, or by threading into a tapped (pre-threaded) hole. They are the backbone of mechanical assemblies in automotive, construction, infrastructure, solar, and industrial sectors.
Key fact: Hex bolts account for the majority of fastener consumption globally. Their simple, robust geometry allows easy tightening with standard tools, making them the go-to choice for high-load structural applications.
At New Star Industries, we have manufactured hex bolts since 1961 — supplying automotive OEMs, railway contractors, solar EPC companies, and pre-engineered building (PEB) manufacturers across India and for export.
The terms are often used interchangeably, but there is a technical distinction in engineering standards:
| Parameter | Hex Bolt | Hex Screw |
|---|---|---|
| Thread coverage | Partial (half thread) | Full thread to head |
| Standard reference | DIN 931 / ISO 4014 | DIN 933 / ISO 4017 |
| Typical use | With nut & washer, structural joints | Threaded holes, through-bolting |
| Shank | Unthreaded grip length present | Fully threaded throughout |
| Load type | Shear & tension loads | Primarily tension / clamping |
In practice, both are driven by the same hex wrench and are often called "hex bolts" generically. New Star Industries manufactures both half-thread (DIN 931) and full-thread (DIN 933) variants across all sizes and grades.
Not all hex bolts are the same. The type you need depends on the application, load, environment, and standard required. Here are the main categories:
Partially threaded shank. Ideal for through-bolting with a nut. Resists shear loads effectively. Follows DIN 931 / ISO 4014 / IS 1364 Part 1.
Thread runs the entire shank length. Best for bolting into tapped holes or where maximum thread engagement is required. Follows DIN 933 / ISO 4017 / IS 1364 Part 2.
Larger head and nut dimensions. Designed for high-load steel structures, PEB buildings, and bridges. Follows IS 3757 / ASTM A325.
Grade 8.8 or 10.9. Heat-treated for maximum strength. Used in automotive, infrastructure, and critical structural assemblies.
Often hot-dip galvanized or ZAC coated for outdoor corrosion resistance. Used in solar panel mounting and pre-engineered building frames.
Anchor bolts embedded in concrete. Used in machinery installation, structural columns, and civil infrastructure bases.
The raw material used in hex bolt manufacturing determines its mechanical properties — strength, ductility, corrosion resistance, and suitability for specific environments.
New Star Industries uses spectrometer-verified (Spectro Analysis) raw materials for every production batch, ensuring consistent alloy composition and traceability — a requirement under our IATF 16949:2016 certification.
Our hex bolts are produced through cold forging (for M6–M24) and hot forging (for M30 and above), followed by thread rolling, heat treatment (for grades 8.8 and above), and surface coating. Every batch undergoes hardness testing, proof load testing, and dimensional inspection before dispatch.
Available in M6–M64 | Grade 4.6 to 10.9 | Multiple coatings | IATF certified supply
Order Now / Send EnquiryThe grade of a hex bolt indicates its mechanical strength — specifically the tensile strength and yield strength of the material. The grade marking is embossed on the bolt head. New Star Industries manufactures the full range:
| Grade | Min. UTS (MPa) | Min. Yield (MPa) | Elongation (%) | Typical Application |
|---|---|---|---|---|
| 4.6 | 400 | 240 | 22 | General construction, light machinery |
| 5.6 | 500 | 300 | 20 | Light structural, civil work |
| 6.8 | 600 | 480 | 12 | General industrial, equipment |
| 8.8 | 800 | 640 | 12 | Automotive, PEB, infrastructure |
| 10.9 | 1000 | 900 | 9 | Heavy automotive, high-load structures |
How to read a grade: In "8.8", the first digit (8) × 100 = minimum UTS in MPa. The second digit (8) × 10% of UTS = yield strength. So 8.8 = 800 MPa UTS, 640 MPa yield.
The right coating protects hex bolts from corrosion, reduces friction, and extends service life. New Star Industries offers the following coatings:
Black/grey finish. Excellent oil retention and paint adhesion. Standard for automotive and industrial applications.
Dark grey finish. Superior hardness and wear resistance. Preferred in engine components and high-friction environments.
Bright silver finish. Standard corrosion protection for general industrial and construction fasteners.
RoHS-compliant, eco-friendly. Required by automotive OEMs and export customers. Equivalent corrosion protection.
1000+ hours salt spray resistance. Ideal for solar structures, outdoor PEB, and coastal environments.
Maximum outdoor corrosion protection. Standard for railway, NHAI highway, and long-life infrastructure fasteners.
Hex bolts are used across virtually every industry. Key sectors supplied by New Star Industries:
Engine assemblies, chassis, suspension, axles, body-in-white. Grade 8.8 & 10.9 with trivalent zinc or ZAC coating.
Pre-engineered buildings, steel structures, mezzanine floors. Heavy hex structural bolts, HDG or ZAC coated.
RDSO-approved supply for track components, coach assembly, and rail bridges. Hot dip galvanized and high tensile grades.
Mounting structures, torque tubes, foundations. ZAC-coated Grade 8.8 bolts for 25+ year outdoor service life.
NHAI-approved fastener supply for flyovers, bridges, highway barriers, and sign structures.
Equipment mounting, base frames, gearboxes, pumps. Full range of grades and sizes for OEM and MRO supply.
Standard metric hex bolt dimensions as per ISO 4014 / DIN 931. New Star Industries manufactures the full range from M6 to M64.
| Size | Thread Pitch (mm) | Width Across Flats (mm) | Head Height (mm) | Min Length (mm) | Max Length (mm) |
|---|---|---|---|---|---|
| M6 | 1.0 | 10 | 4.0 | 12 | 100 |
| M8 | 1.25 | 13 | 5.3 | 16 | 150 |
| M10 | 1.5 | 17 | 6.4 | 20 | 200 |
| M12 | 1.75 | 19 | 7.5 | 25 | 200 |
| M16 | 2.0 | 24 | 10.0 | 30 | 300 |
| M20 | 2.5 | 30 | 12.5 | 40 | 300 |
| M24 | 3.0 | 36 | 15.0 | 50 | 400 |
| M30 | 3.5 | 46 | 18.7 | 60 | 400 |
| M36 | 4.0 | 55 | 22.5 | 80 | 500 |
| M42 | 4.5 | 65 | 26.0 | 100 | 500 |
| M48 | 5.0 | 75 | 30.0 | 100 | 500 |
| M56 | 5.5 | 85 | 35.0 | 120 | 500 |
| M64 | 6.0 | 95 | 40.0 | 140 | 500 |
Custom lengths and special dimensions available on request. Contact our technical sales team for non-standard requirements.
We manufacture hex bolts M6 to M64 in all grades — custom specifications welcome.
Order Now / Get a QuoteNew Star Industries manufactures hex bolts in compliance with the following national and international standards:
| Standard | Description | Application |
|---|---|---|
| IS 1364-1 | Hex head bolts — half thread | General structural & industrial use |
| IS 1364-2 | Hex head screws — full thread | Tapped holes, machinery |
| IS 3757 | High strength structural bolts | Steel structures, bridges, PEB |
| IS 6623 | High strength structural nuts | Paired with IS 3757 bolts |
| Standard | Description | Thread Type |
|---|---|---|
| DIN 931 | Hex bolt — partial thread | Half thread |
| DIN 933 | Hex screw — full thread | Full thread |
| DIN 960 | Hex bolt — fine pitch, partial thread | Fine thread |
| DIN 961 | Hex bolt — fine pitch, full thread | Fine thread |
| Standard | Description | Equivalent DIN |
|---|---|---|
| ISO 4014 | Hex bolts — product grades A & B, partial thread | DIN 931 |
| ISO 4017 | Hex screws — product grades A & B, full thread | DIN 933 |
| ISO 4016 | Hex bolts — product grade C | — |
| ISO 4018 | Hex screws — product grade C | — |
| Standard | Description |
|---|---|
| EN 14399 | High-strength structural bolt assemblies for preloading — steel construction across Europe |
| ASTM A325 | High-strength bolts for structural steel joints — US / export requirements |
| ASTM A490 | Heat-treated steel structural bolts — higher strength than A325 |
New Star Industries is IATF 16949:2016 and ISO 14001:2015 certified, and supplies fasteners per customer-specified national and international standards. We are approved by Indian Railways (RDSO) and NHAI for infrastructure supply.
Correct torque ensures proper clamping force without damaging the bolt or joint. Approximate reference values for Grade 8.8 and 10.9 hex bolts with standard lubrication (μ = 0.12):
| Bolt Size | Grade 8.8 (Nm) | Grade 10.9 (Nm) | Recommended Wrench |
|---|---|---|---|
| M6 | 9–11 | 13–15 | 10 mm |
| M8 | 22–25 | 31–36 | 13 mm |
| M10 | 44–50 | 62–70 | 17 mm |
| M12 | 76–87 | 107–122 | 19 mm |
| M16 | 185–210 | 260–295 | 24 mm |
| M20 | 360–410 | 510–580 | 30 mm |
| M24 | 625–710 | 880–1000 | 36 mm |
| M30 | 1200–1360 | 1690–1920 | 46 mm |
| M36 | 2100–2380 | 2960–3360 | 55 mm |
Note: Always refer to the design engineer's specification or equipment OEM guidelines. Values vary with lubrication, surface finish, and joint material.
Vikram Bhamra - CEO, New Star Industries
Vikram Bhamra is the CEO of New Star Industries, a third-generation manufacturing company specializing in high-performance fasteners for automotive, infrastructure, and heavy engineering applications. After graduating in Business Management from Canada in 2010, he returned to India in 2011 to lead and modernize the family enterprise. With 14+ years of hands-on experience, he has driven advancements in cold forging, zinc flake coating, and precision heat treatment. In 2024, he founded New Star AutoComp, expanding cold forged fasteners into automotive OEMs, railway bridges, PEB, and heavy engineering sectors with globally compliant fastening solutions.
