1. Standards and types
DIN 933: Full thread external hexagon bolt, with all screw parts threaded, suitable for scenarios that require full-length threaded fixation.
DIN 931: Half threaded external hexagon bolt, with a smooth rod section (no thread) at the end of the screw, and a thread length of about 1.5 times the nominal diameter of the bolt, suitable for situations that require shear resistance or precise positioning.
Standard system: German Industrial Standards (DIN), compliant with metric (millimeter) specifications, widely used in European and international markets, compatible with ISO international standards (such as ISO 4014/4017).

2. Structural characteristics
Head: Standard hexagonal design, compliant with DIN 934 standard, easy to install using a hex wrench or socket tool.
Thread: Metric coarse thread (standard M series, such as M6, M12, etc.), thread angle 60 °, consistent with ISO universal standards.

Material and grade:
Material: Carbon steel (such as C45, with high surface hardness), stainless steel (such as A2-70, A4-80), or alloy steel.
Strength grade: 4.8 grade, 8.8 grade, 10.9 grade, etc. (numerical values represent the ratio of tensile strength to yield strength, such as 8.8 grade being 800 MPa tensile strength).

3. Specification parameters
Example annotation: For example, M12 × 50 represents a nominal diameter of 12mm and a length of 50mm (from the bottom of the head to the end of the screw).
Surface treatment: galvanizing (electroplating, hot-dip galvanizing), Dacromet, phosphating or natural color oxidation (blackening) to enhance corrosion resistance.

4. Application scenarios
Mechanical manufacturing: equipment assembly, heavy machinery connection.
Automotive industry: high-strength fasteners for engines, chassis, etc.
Construction engineering: Steel structures, bridge connections, especially widely used in the European market.
Electronics and Home Appliances: Standardized Fixation of Medium Load Components.

5. Comparison with other standards
Compared to the American standard (ASTM/SAE): different units (metric vs. imperial), thread standard (DIN metric coarse thread vs American standard UNC/UNF), strength identification (such as 8.8 corresponding to American standard Grade 5).
Compared to the national standards (GB 5782/5783), DIN standards have similar parameters to GB standards, but there may be differences in dimensional tolerances and testing requirements.

6. Precautions
Select strength grade based on load requirements (such as grade 8.8 for moderate dynamic loads).
The bare rod section (DIN 931) can reduce thread wear and is suitable for situations that require shear force or positioning.
Surface treatment needs to be matched with the environment (if it is humid, stainless steel A4-80 or galvanized treatment should be preferred).

Summary of Characteristics: DIN hexagon bolts are known for their high precision and standardization, and are a universal fastener solution in the European mechanical and engineering fields.