Carbon Steel Hex Bolt — Factory Direct Supplier | Huaxia-Steel

Huaxia-Steel manufactures and exports industrial-grade carbon steel hex bolts for structural, mechanical, and general fastening applications. Our hex bolt product line covers ASTM A307, ASTM A325, ASTM A490, DIN 931, DIN 933, and ISO 4014/4017 standards with full certification and customization capabilities.

Product Overview

The hex bolt — named for its six-sided head — is the most widely used fastener in steel construction and machinery assembly. Carbon steel hex bolts offer an optimal balance of strength, cost-effectiveness, and availability across standard and specialty sizes.

Huaxia-Steel supplies hex bolts in full thread (DIN 933 / ISO 4017) and partial thread (DIN 931 / ISO 4014) configurations, with diameters from M5 to M64 and 1/4″ to 2-1/2″.

Specifications and Dimensions

Parameter	Specification
Diameter Range	M5 to M64 (metric); 1/4″ to 2-1/2″ (imperial)
Length Range	10mm to 600mm; 1/2″ to 24″
Thread Pitch	Coarse (standard), fine, extra-fine per request
Head Style	Hexagon head (standard), heavy hex, flange hex
Drive	External hex (wrench), socket head (optional)
Thread Type	Full thread, partial thread, double end stud
Tolerance Class	6g (standard), 6h, 4h6h per requirement

Standard Dimensions (Metric — DIN 933 Full Thread)

Size (d)	Pitch	s (mm)	e (mm)	k (mm)	Max Length (mm)
M6	1.0	10	11.05	4.0	200
M8	1.25	13	14.38	5.3	200
M10	1.5	17	18.90	6.4	200
M12	1.75	19	21.10	7.5	260
M16	2.0	24	26.75	10.0	260
M20	2.5	30	32.95	12.5	260
M24	3.0	36	39.55	15.0	300
M30	3.5	46	50.85	18.7	300
M36	4.0	55	60.79	22.5	300

Material Grades and Mechanical Properties

Grade/Class	Standard	Proof Load (MPa)	Tensile Strength (MPa)	Application
Class 4.8	ISO 898-1	310	420	General fastening, low stress
Class 5.8	ISO 898-1	380	520	General machinery
Class 8.8	ISO 898-1	600	800	Structural, automotive
Class 10.9	ISO 898-1	830	1,040	Heavy machinery, engines
Class 12.9	ISO 898-1	970	1,220	High-stress applications
ASTM A307 Gr.A	ASTM A307	—	415	General construction
ASTM A307 Gr.B	ASTM A307	—	415-725	Flanged joints
ASTM A325 Type 1	ASTM A325	—	≥827	Structural steel connections
ASTM A490	ASTM A490	—	≥1,034	Heavy structural connections

Chemical Composition (Class 8.8 / ASTM A325 Type 1)

Element	Composition (%)
Carbon (C)	0.25-0.55
Manganese (Mn)	0.30-0.90
Phosphorus (P)	≤0.040
Sulfur (S)	≤0.050
Silicon (Si)	≤0.35
Boron (B)	≤0.003 (for boron steel)

Surface Finishes and Coatings

Finish	Standard/Process	Corrosion Resistance	Typical Application
Plain / Black oxide	Oil dip or chemical blackening	Indoor, short-term	Internal machinery
Zinc plated (clear)	Electroplating, 5-8 μm	Moderate, indoor	General construction
Zinc plated (yellow)	Electroplating + chromate	Good, outdoor protected	Automotive, machinery
Hot-dip galvanized	ASTM A153, 50-85 μm	Excellent, outdoor	Infrastructure, bridges
Dacromet / Geomet	Dip-spin coating	Superior, salt spray 500h+	Automotive, marine
PTFE / Xylan coating	Spray or dip	Chemical resistant	Chemical processing

Manufacturing Process

1. Raw material: Cold heading quality wire rod (CHQ) or hot rolled bar
2. Cold forging: Multi-station cold header forms head and partial shank
3. Thread rolling: Rolled threads (stronger than cut) formed under pressure
4. Heat treatment: Quenching and tempering for Grade 8.8+ (Class 10.9, 12.9)
5. Surface finishing: Cleaning, coating per specification
6. Inspection: Dimensional, mechanical, surface quality verification
7. Thread protection: Plastic caps applied to prevent damage

Applications

• Steel structures: Building frames, bridges, towers (A325, A490)
• Machinery assembly: Equipment bases, gearbox housings, bearing caps
• Automotive: Chassis, suspension, engine mounting (Class 10.9)
• Oil and gas: Flange connections, pressure vessel bolting
• Railway: Track fastening, signal equipment mounting
• Renewable energy: Wind turbine tower sections, solar mounting

Quality Assurance

• Dimensional inspection: Thread gauges (GO/NO-GO), calipers, micrometers
• Mechanical testing: Tensile test, wedge tensile test, proof load test
• Hardness testing: Rockwell C or Vickers per ISO 898-1
• Surface inspection: Visual per ISO 6157-1; magnetic particle if specified
• Coating thickness: Eddy current or XRF measurement
• Salt spray testing: ASTM B117 for coated fasteners (48-96 hours)
• Mill certificates: EN 10204 3.1 standard; 3.2 with third-party inspection

Packaging and Shipping

• Standard: 25kg cartons with plastic liner, palletized
• Bulk: 500-1,000kg wooden crates for large orders
• Small orders: Plastic bags with labels, packed in master cartons
• Thread protectors on all threaded fasteners
• Desiccant included for ocean freight
• Marking: Size, grade, quantity, batch number, standard

Ordering Information

Please provide the following for accurate quotation:

• Diameter and thread pitch (e.g., M16 × 2.0, 3/4″-10 UNC)
• Length (measured from underside of head to end of thread)
• Grade/Class (4.8, 8.8, 10.9, A307, A325, A490)
• Standard (DIN 931, DIN 933, ISO 4014, ASTM A325)
• Finish (plain, zinc plated, hot-dip galvanized, Dacromet)
• Quantity and delivery schedule
• Special requirements (certificates, testing, packaging)

Need carbon steel hex bolts for your project? Contact Huaxia-Steel for competitive pricing, technical support, and on-time delivery of certified fasteners.