What are the common models of German standard bolts?

2025-07-28

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.

Part One: The Genetic Code of German Standard Bolts

The German Industrial Standard (DIN) is renowned for its precise tolerances and performance classification. Its core model system for hexagon socket bolts consists of three major categories:

Basic model

DIN 931 (Half Thread) : Head alignment tolerance ±0.15mm, thread length b=2d+6mm (when d≤125mm)

DIN 933 (Full Thread) : Suitable for full-bar force-bearing scenarios, with a tensile strength of up to 1220MPa (12.9 grade) for M12 specification

DIN 934 (Hexagonal nut) : Used in conjunction with bolts, the opposite side dimension S=M12 corresponds to 19mm

High-strength model

DIN 6914: Special bolts for wind power, 12.9 grade +HV390 hardness, flange surface design to prevent loosening

DIN 6921: Hexagonal flange face, M8 specification head thickness 8.1mm, integrated gasket function

Special model

DIN 34800 (Guide end bolt) : Rapid positioning on the automated production line, thread end Angle 30°

DIN 603 (Carriage Bolt) : Countersunk head and square neck structure, suitable for rail vehicle assembly

(Chart: German Standard Bolt Head size comparison table, highlighting the k/s tolerance zone of M6-M24 specification)

Part Two: The Golden Rule for Model Selection

2.1 Material and performance match

Carbon steel grade 4.8 (DIN 933) : Suitable for static load cabinet assembly, with a 40% cost reduction

Alloy steel grade 10.9 (DIN 931) : Zero loosening at the connection points of the automotive chassis after 2000 hours of vibration test

Stainless steel A2-70: Anti-corrosion solution for chemical equipment, salt spray test > 1,000 hours

2.2 Practical Cases of Dimensional Accuracy

The battery pack of a certain new energy vehicle adopts DIN 933-M8×25 to replace the national standard parts:

Reduce weight by 12% while increasing shear strength by 18%

The height tolerance of the hexagonal head is ±0.1mm, enabling automatic tightening by a robot

Part Three: Breakthroughs in Industry Pain Points

Anti-loosening revolution

DIN 6921 flange bolts in photovoltaic support applications:

The loosening rate under wind load conditions decreased by 76%

The integrated design reduces the usage of gaskets

Assembly efficiency has jumped

Tesla's Berlin factory adopts DIN 931-10.9 grade:

The robot's visual recognition of head chamfers (0.2mm standard) has increased the positioning speed by 30%

Part Four: Future Trends

DIN EN ISO 4017 environmentally friendly bolts newly released in 2025:

Bio-based coating technology reduces carbon emissions by 50%

It is fully compatible with the traditional DIN 931 and no production line modification is required

(Technical Parameter Table: Strength attenuation curve of 12.9 grade bolts under operating conditions of -40℃ to 150℃)