Black M8 M12 Carbon steel Flat head Philip sclotted tapping metal screws Class4. 8 Grade4.8

• Ordinary self-tapping screws: Feature 'self-tapping thread' (wide thread), mostly surface plated.
• Self-cutting tapping screws: Include cross recessed pan head, countersunk head, raised countersunk head, and hexagonal head variants.
• Self-extruding tapping screws: Typically use machine thread with triangular cross-section for high-speed assembly.
• Self-drilling tapping screws: Designed with self-tapping or machine thread for direct drilling applications.
• Metal drive screws: Feature multi-head special thread primarily following US standards.
• Wallboard tapping screws: Include trumpet head with cross groove and 60° tooth angle, often phosphated.
• Fibreboard nails: Available in various head styles with Z-type cross slot, typically plated.
• Combination self-tapping screws: Combine standard screws with washers for enhanced functionality.
• Specialty variants: Include double lead, different pitch threads, sealed threads, and composite groove designs.

Bolt performance level 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9 and other 10 grades;

Among them, 8.8 and above bolts made of low-carbon alloy steel or medium-carbon steel and heat treatment (quenching, tempering), collectively referred to as high-strength bolts, and the rest collectively referred to as ordinary bolts.

Bolt performance level marking has two parts of the digital composition, respectively, that the nominal tensile strength of the bolt material value and flexural strength ratio value.
The meaning of 4.8 is

Tensile strength Rm=4×100 N/mm2=400 N/mm2=400MPa

Yield strength Re = 400 × 0.8 = 320MPa

• Manufactured from carburized steel (99%), with stainless steel or non-ferrous options available
• Heat-treated for optimal performance - carbon steel screws are carburized, stainless steel screws are solution-hardened
• High surface hardness with tough core ("soft outside steel") for superior fastening performance
• Surface protection through plating or phosphate treatment (for wallboard screws)
• Produced using high-speed cold heading and thread rolling machines for consistent quality

• Enhanced rust prevention: Iron tetraoxide film inhibits red rust formation, with optional oil treatment for added protection
• Improved durability: Chemically bonded surface treatment resists flaking compared to plating or painting
• Better tool compatibility: Maintained surface oil improves sliding properties for tools and machine parts