Specializing in the production of special precision screws and nuts of various standards such as Chinese standard GB, Japanese standard JIS, British BS, American ANSI and ISO.
At present, the smallest screw diameter that our company can produce is 0.4mm, the shortest is 0.4mm, and the longest is 300CM.
2025-07-12 16:31:32
Flat head machine screws, also known as countersunk screws, are threaded fasteners with a flat top surface and a conical bearing surface that tapers at an angle of 82° or 90°. These screws are designed to sit flush with or below the surface of the material being fastened, creating a smooth finish. The head features a single slot or Phillips drive (though other drive types like Torx are available) and is typically made from materials such as stainless steel (Grade 304 or 316), carbon steel (Grade 2, 5, or 8), or brass. Thread sizes range from #0 (1.52 mm diameter) to ¾" (19.05 mm diameter), with lengths varying between 1/8" (3.18 mm) to 6" (152.4 mm).
Head Angle: Standard angles are 82° (common in the US) or 90° (metric standards). The angle must match the countersunk hole for proper seating.
Drive Types: Slotted, Phillips (most common with a #1 or #2 size), Hex socket (Allen), or Torx (T10-T40). Torx drives offer up to 10x more torque transmission compared to Phillips.
Material Strength: Carbon steel screws have tensile strengths ranging from 60,000 psi (Grade 2) to 150,000 psi (Grade 8), while stainless steel (18-8) offers 70,000-90,000 psi.
Thread Pitch: Coarse (UNC) or fine (UNF) threads. For example, a #10 screw has 24 threads per inch (TPI) in UNC and 32 TPI in UNF.
Corrosion Resistance: 316 stainless steel provides >1,000 hours in salt spray tests (ASTM B117), compared to 96 hours for zinc-plated carbon steel.
Flat head machine screws are used where a flush surface is critical:
Aerospace: Fastening aluminum panels (e.g., 0.040" thick) with #6-32 screws (tensile strength 1,800 lbs).
Automotive: Attaching trim pieces with M4x0.7 screws (torque specification: 2.2 Nm ±10%).
Electronics: Securing PCB mounts using #2-56 screws (shear strength 290 lbs).
Furniture: Joining wood with #8-32 screws (pull-out resistance 150 lbs in hardwood).
Marine: 316 stainless screws for deck hardware (withstands 5% NaCl environments).
Proper care extends screw life and maintains performance:
Cleaning: Use a wire brush (0.3 mm bristles) for carbon steel or nylon brush for stainless steel. Ultrasonic cleaners (40 kHz frequency) remove debris from threads.
Lubrication: Apply molybdenum disulfide grease (0.5-1.0 mg/in²) to reduce friction. For high-temperature applications, use nickel-based anti-seize (up to 2,400°F/1,315°C).
Torque Control: Use a calibrated torque wrench. Example: A 1/4"-20 screw in aluminum requires 6.2 ft-lbs dry or 4.3 ft-lbs lubricated.
Corrosion Prevention: For steel screws, apply zinc plating (5-15 µm thick) or Dacromet coating (8-12 µm).
Inspection: Check for thread wear using GO/NO-GO gauges. Replace if pitch diameter exceeds +0.002" tolerance.
Pre-drill holes to 80% of minor diameter (e.g., 2.8 mm for M3 screw).
Countersink angle must match screw head angle (±1° tolerance).
Use CR-V screwdrivers (Rockwell C52-56 hardness) to prevent cam-out.
In soft materials, add washer (0.8 mm thick x 5 mm ID) to prevent pull-through.
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