Carbon Steel Hex Bolt — Factory Direct Supplier | Huaxia-Steel
Carbon steel hex bolts are the most widely used threaded fastener in structural steel, machinery assembly, automotive, and general fabrication. Huaxia-Steel manufactures hex head bolts from M5 to M64 and ¼ inch to 2½ inches, in strength grades 4.8 through 12.9 and ASTM A307 / A325 / A490 specifications, with plain, zinc-plated, hot-dip galvanized, and dacromet finishes. All bolts are supplied with mill test certificates and optional third-party inspection.
Product Overview
Our hex bolts are produced by multi-station cold forging or hot forging followed by CNC thread rolling, depending on diameter and strength grade. Cold forging is used for standard sizes up to M24 and grades 4.8–8.8, delivering excellent dimensional consistency and surface finish. Hot forging is used for larger diameters (M27+) and high-strength grades 10.9–12.9, where the material must be worked at elevated temperature to achieve full density and fibrous grain flow. Threads are rolled rather than cut, producing a work-hardened surface with superior fatigue resistance and consistent pitch diameter.
Specifications
| Parameter | Details |
|---|---|
| Diameter | M5 – M64; ¼” – 2½” (custom up to M100) |
| Length | 10 mm – 600 mm; custom up to 3,000 mm |
| Thread | Full thread, partial thread, coarse (ISO/UNC), fine (UNF) |
| Head style | Hex head DIN 931/933, heavy hex ASME B18.2.1, flange head |
| Strength grades | 4.8, 5.8, 6.8, 8.8, 10.9, 12.9; ASTM A307 Gr A/B, A325, A490 |
| Materials | Q235, C1022, C1045, 40Cr, 35CrMo, SCM435, 42CrMo |
| Finish | Plain (oiled), zinc plated (blue/white/yellow), HDG, dacromet, PTFE |
| Standards | DIN 931/933/6914, ISO 4014/4017, ASME B18.2.1, GB/T 5782/5783 |
Strength Grade Selection Guide
| Grade | Material | Typical use |
|---|---|---|
| 4.8 / A307 | Low-carbon steel (Q235) | General construction, shelving, wood-to-steel |
| 8.8 | Medium-carbon steel (C1045) | Machinery, automotive, structural bolting |
| 10.9 | Alloy steel (40Cr, SCM435) | Heavy machinery, engine beds, high-stress joints |
| 12.9 | Alloy steel (42CrMo) | Presses, cranes, critical safety joints |
Manufacturing Standards and Quality Control
Production is controlled under ISO 9001 and IATF 16949 (automotive) where applicable. Incoming wire rod or bar is checked for chemistry and tensile properties. Forging parameters (temperature, press force, dwell time) are monitored per die station. Thread rolling is verified with ring gauges and optical pitch measurement. Heat treatment (quench and temper for grades 8.8 and above) uses continuous atmosphere-controlled furnaces with automatic hardness sampling. Final inspection includes dimensional checks, torque-tension testing on representative samples, salt-spray testing for coated batches, and magnetic particle inspection for Grade 12.9.
Applications
- Steel building and bridge structural connections
- Machinery bases, gearboxes, and press assemblies
- Automotive chassis, suspension, and powertrain
- Wind turbine tower and nacelle bolting
- Railway track fastening and switchgear
- General fabrication, maintenance, and MRO inventory
Packaging and Shipping
Bolts are bulk-packed in 25 kg cartons or 1-ton wooden crates, with plastic trays for large diameters to prevent thread damage. Each package is labeled with grade, size, batch number, and standard. For sea freight, cartons are palletized and stretch-wrapped with VCI film. Coated bolts (zinc, HDG) are packed with desiccant to prevent white rust. Custom kit packing (mixed sizes per project BOM) is available on request.
Request a Hex Bolt Quotation
Huaxia-Steel supplies carbon steel hex bolts from M5 to M64 in grades 4.8–12.9 with full MTC, dimensional report, and optional SGS/BV inspection. Send us your BOM for a same-day quote with drawings and delivery schedule.
