Carbon Steel Socket Head Cap Screw — Factory Direct Supplier | Huaxia-Steel

Huaxia-Steel manufactures precision carbon steel socket head cap screws (SHCS) for machinery, tooling, automotive, and precision engineering applications. Our SHCS product line conforms to DIN 912, ISO 4762, and ANSI B18.3 standards with strength classes from 8.8 to 12.9 and surface finishes including black oxide, zinc plating, and nickel plating.

Product Overview

The socket head cap screw features a cylindrical head with an internal hex drive (Allen key), offering high torque transmission capability and a compact head profile ideal for recessed installations. Carbon steel SHCS delivers superior tensile strength compared to standard hex bolts of equivalent size, making it the preferred choice for high-stress mechanical assemblies.

Huaxia-Steel produces SHCS with rolled threads for enhanced fatigue resistance and precision ground bodies for close-tolerance applications.

Specifications and Dimensions

Parameter	Specification
Diameter Range	M3 to M36 (metric); #0 to 1-1/2″ (imperial)
Length Range	4mm to 300mm; 1/8″ to 12″
Head Style	Cylindrical socket head (standard), low head, button head, flat head
Drive	Hex socket (Allen), TORX, Phillips (custom)
Thread	Metric coarse (standard), fine, UNC, UNF
Thread Generation	Rolled (standard), ground (precision)
Tolerance	6g (standard), 4h (precision)

Standard Dimensions (DIN 912 — Metric)

Size (d)	Dk (mm)	K (mm)	S (mm)	t (mm)	b (ref)
M3	5.50	3.00	2.50	1.3	18
M4	7.00	4.00	3.00	2.0	20
M5	8.50	5.00	4.00	2.5	22
M6	10.00	6.00	5.00	3.0	24
M8	13.00	8.00	6.00	4.0	28
M10	16.00	10.00	8.00	5.0	32
M12	18.00	12.00	10.00	6.0	36
M16	24.00	16.00	14.00	8.0	44
M20	30.00	20.00	17.00	10.0	52
M24	36.00	24.00	19.00	12.0	60

Material Grades and Mechanical Properties

Property	Class 8.8	Class 10.9	Class 12.9
Tensile Strength (MPa)	800	1,000	1,200
Yield Strength (MPa)	640	900	1,080
Hardness (HRC)	22-32	32-39	39-44
Elongation (%)	12	9	8
Surface Hardness (HV)	250-320	320-390	385-435

Chemical Composition (Class 12.9)

Element	Composition (%)
Carbon (C)	0.30-0.50
Manganese (Mn)	0.50-0.90
Silicon (Si)	0.10-0.40
Phosphorus (P)	≤0.025
Sulfur (S)	≤0.025
Chromium (Cr)	0.50-1.00
Nickel (Ni)	≤0.70
Molybdenum (Mo)	0.15-0.40
Vanadium (V)	≤0.20

Surface Finishes

Finish	Process	Appearance	Salt Spray (hrs)
Black oxide	Chemical conversion	Matte black	12-24
Zinc plated (blue)	Electroplating + trivalent passivation	Blue-white bright	48-72
Zinc plated (yellow)	Electroplating + hexavalent passivation	Iridescent yellow	72-96
Zinc-nickel alloy	Alloy electroplating	Silver-gray	240-500
Nickel plated	Electroplating	Bright silver	96-144
Dacromet / Geomet	Dip-spin zinc flake	Silver-gray matte	500-1,000
Phosphate coated	Manganese phosphate	Dark gray	24-48 (with oil)

Manufacturing Process

1. Wire selection: Cold heading quality (CHQ) wire rod, spheroidized annealed
2. Cold heading: Multi-die cold former produces head and shank in 3-5 stations
3. Thread rolling: Flat die or planetary thread rolling for grain-flow continuity
4. Heat treatment: Austenitizing 850-880°C, oil quench, tempering 400-500°C
5. Surface finishing: Cleaning, coating per specification
6. Final inspection: Dimensional, mechanical, and surface quality checks
7. Anti-corrosion packaging: VCI bags or desiccant with sealed containers

Applications

• Machine tools: Spindle housings, fixture clamping, tool holders
• Automotive: Engine components, transmission assemblies, brake systems
• Precision equipment: Robotics, CNC machines, optical instruments
• Mold and die: Injection mold assembly, die casting tools
• Aerospace: Secondary structures, ground support equipment
• Electronics: Server racks, telecommunications enclosures

Quality Assurance

• Dimensional: Optical sorting, CMM verification of critical dimensions
• Mechanical: Tensile testing per ISO 898-1; proof load testing
• Hardness: Rockwell C testing on head and shank
• Surface: Visual inspection per ISO 6157-3; decarburization check
• Thread: GO/NO-GO thread gauge inspection
• Coating: Thickness measurement (XRF, eddy current); adhesion test
• Corrosion: Neutral salt spray (NSS) per ASTM B117
• Documentation: EN 10204 3.1 certificate; PPAP available on request

Packaging and Shipping

• Standard: 1-5kg plastic bags with desiccant, master cartons
• Bulk: 20-25kg cartons on plywood pallets
• Precision grade: Individual compartment trays preventing contact damage
• Export packaging: Vacuum-sealed VCI bags for ocean freight
• Labeling: Size, grade, quantity, batch number, standard, manufacturing date

Ordering Information

For quotation, please specify:

• Size (diameter × length, e.g., M10 × 40mm)
• Strength class (8.8, 10.9, or 12.9)
• Standard (DIN 912, ISO 4762, ANSI B18.3)
• Thread type (coarse, fine, UNC, UNF)
• Surface finish
• Quantity and delivery requirements
• Certificate level (3.1, 3.2, PPAP)

Request your carbon steel socket head cap screw quotation today. Contact Huaxia-Steel with your specifications for competitive pricing and reliable delivery.