hex bolt fine thread DIN933

Prioritize tapping for mass production, standard parts, through holes, low cost and high speed. Prioritize thread milling for deep blind holes, difficult-to-machine materials (e.g., titanium alloy, stainless steel), non-standard threads, mixed production of multiple specifications, and high precision requirements.

Grade 4.8: Low carbon steel, tensile strength ≥400MPa, yield strength ≥320MPa, for general light-load and non-critical connections. Grade 8.8: Medium carbon steel quenched and tempered, tensile strength ≥800MPa, yield strength ≥640MPa, for general heavy-load and main equipment. Grade 12.9: Alloy steel, tensile strength ≥1200MPa, yield strength ≥1080MPa, for high-strength, vibration/impact conditions (e.g., construction machinery, automotive chassis).

Spring washers (GB/T 93): Elastic preload, general light vibration, low cost. Lock washers (internal/external teeth, GB/T 861/862): Teeth embedment, stronger anti-loosening, suitable for medium to high strength. Thread adhesives (anaerobic adhesives): Permanent/semi-permanent locking, sealing and rust prevention, suitable for critical connections that are not frequently disassembled.

6g: Commonly used for external threads (bolts/screws), medium precision, general assembly. 6H: Commonly used for internal threads (nuts), medium precision, matches 6g external threads. 5g6g: High-precision combination for external threads (pitch diameter 5g, major diameter 6g), used in scenarios with high precision and anti-loosening requirements.

Format: Type + Standard No. + Specification + Surface Treatment. Example: Bolt BOLT-GB5783-M10×30-8.8-Zn; Nut NUT-GB6170-M10-8H-Zn; Washer WASHER-GB97.1-10-A-Zn. Must include: standard number, specification, strength/precision, surface treatment to ensure consistency in procurement and assembly.

Cut threads: Cut material fibers, grain fracture, poor fatigue resistance. Rolled threads: Cold work hardening + continuous fibers, grains distributed along thread flow lines, tensile/shear/fatigue resistance increased by 30%–100%, especially suitable for high-strength standard fasteners.