What types of hex socket bolts are there?

2025-07-30

David Dai

sales

Ningbo Zhongli Bolts Manufacturing Co., Ltd. founded in 2003, is a professional manufacturer of high-strength fasteners in different specifications for various models, which is covering an area of about 10,000 square meters, registered capital of 1500,000 RMB, with the total annual productivity of 8,000 tons per year. The company has set up several sales branches in different provinces in China. Meanwhile, the company's products are exported to Europe, USA, Middle East, Africa, Southeast Asia and other regions.

In the microcosm of mechanical manufacturing, an Allen bolt with a diameter of less than one centimeter might be the key to ensuring the rapid speed of high-speed trains and the launch of spacecraft. This type of fastener with a hexagonal groove on the top has become a "universal screw" in the industrial field due to its strong torque resistance and small space occupation. This article will systematically analyze its classification system and application scenarios.

I. Classified by material: From basic steel to space alloy

1. Carbon steel family

Grade 4.8 /8.8: A cost-effective choice for home appliances and furniture

Grade 12.9: The "steel frame" of automotive engines, with a hardness of HRC39-44

2. Stainless steel camp

304 stainless steel: The anti-corrosion guardian for food machinery

316L molybdenum-containing steel: Acid-resistant barrier for chemical equipment

3. Special Materials Group

Titanium alloy: 40% lighter, exclusive for aviation

Nickel-based alloys: Radiation resistance solutions for nuclear power plants

Ii. Classification by Head Shape: Industrial Aesthetics of Geometry

Iii. Surface treatment process: Invisible protective shield

The Three Brothers of Galvanizing：

Blue-white zinc (the most basic)

Color zinc (salt spray resistance for 96 hours)

Black zinc (Special for automotive chassis)

Dacromet technology：

No hydrogen embrittlement risk, salt spray resistance over 1000 hours, standard configuration for high-speed rail bolts

PTFE coating：

Self-lubricating property, anti-biological adhesion for medical devices

Four. Golden Rule of Application Scenarios

1.Automobile manufacturing: The engine block must be treated with 12.9 grade and phosphating

2.Photovoltaic support: Anti-loosening washers are required for specifications above M10

3.Medical equipment: Nickel-containing materials are prohibited (to avoid allergic reactions)

Case: SpaceX Starship Bolt Upgrade Incident in 2024

Musk's team replaced the traditional hex socket with high-temperature resistant Inconel 718 alloy bolts, successfully solving the problem of fastener failure during re-entry into the atmosphere.

V. Guide to Avoiding Pitfalls When Purchasing

1.Size trap：

The thread tolerance difference between the German standard DIN912 and the Chinese standard GB70 can reach 0.2mm

2.Hardness test：

Regular manufacturers should provide third-party test reports (such as SGS).

3.Anti-counterfeiting identification：

The heads of high-quality bolts will be laser-engraved with the material grade and factory logo