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.
2025-06-28 16:16:34
Hex screws, also known as hex cap screws or hex head screws, are fasteners with a hexagonal head designed to be driven by a wrench or socket. Below are the key specifications with professional data:
Head Type: Hexagonal head with a flat bearing surface. Standard head height is 0.866 times the nominal screw diameter (D).
Thread Type: Most hex screws feature Unified National Coarse (UNC) or Unified National Fine (UNF) threads. Metric variants use ISO metric threads.
Material: Typically made from carbon steel (Grade 2, 5, or 8), stainless steel (A2 or A4), or alloy steel with tensile strengths ranging from 60,000 to 180,000 psi.
Surface Finish: Common finishes include zinc plating (5-15 µm), hot-dip galvanizing (50-100 µm), or black oxide coating (1-3 µm) for corrosion resistance.
Size Range: Standard diameters range from M3 (0.5 mm pitch) to M36 (4.0 mm pitch) in metric, or #4-40 to 1-1/2" diameter in imperial sizes.
Torque Values: For a Grade 5, 1/2" diameter hex screw, the recommended torque is 85-100 ft-lbs (115-135 Nm) when lubricated.
Note: The actual specifications may vary depending on the standard (ASTM, ISO, DIN) and manufacturer. Always refer to technical datasheets for critical applications.
Hex screws are widely used in various industries due to their high torque capability and secure fastening:
Automotive Industry: Used in engine components, transmission systems, and chassis assemblies where high tensile strength (Grade 8 or 10.9) is required.
Construction: Structural steel connections often use A325 or A490 heavy hex structural bolts with diameters from 1/2" to 1-1/2".
Machinery: Industrial equipment utilizes hex screws with fine threads (UNF or M fine pitch) for precise adjustment and vibration resistance.
Electronics: Smaller hex screws (M2-M5) with stainless steel (A2-70) construction are common in device enclosures.
Aerospace: Specialized hex screws made from titanium alloys or corrosion-resistant steels meet NAS or MS standards.
Furniture Assembly: Medium-sized hex screws (M6-M12) with zinc plating are common in flat-pack furniture.
Proper maintenance ensures the longevity and performance of hex screws:
Cleaning: Remove dirt and debris using a wire brush or compressed air. For corrosion, use a phosphoric acid-based cleaner followed by rinsing.
Lubrication: Apply anti-seize compound (containing 20-30% copper or nickel) to threads before installation in high-temperature or corrosive environments.
Torque Control: Always use a calibrated torque wrench and follow manufacturer specifications. Under-torquing can lead to loosening, while over-torquing may cause thread stripping (exceeding 75% of proof load).
Corrosion Prevention: For outdoor applications, consider hot-dip galvanized screws with 85 µm coating or stainless steel A4 (316) for marine environments.
Storage: Keep screws in low-humidity environments (below 60% RH) with VCI (Vapor Corrosion Inhibitor) packaging for long-term storage.
Inspection: Regularly check for thread wear (more than 10% material loss), head deformation, or corrosion pits deeper than 0.1 mm.
Critical Note: In safety-critical applications (e.g., aerospace or structural), always follow the manufacturer's maintenance schedule and replace fasteners at recommended intervals.
Correct installation is crucial for optimal performance:
Pilot Holes: For hard materials, drill pilot holes with 75-80% of the screw's minor diameter to prevent cracking.
Thread Engagement: Ensure minimum 1.5 times the screw diameter of thread engagement in the mating part.
Washer Use: Flat washers should have an outer diameter 2 times the screw diameter and hardness at least equal to the screw.
Sequencing: For multiple fasteners, follow a cross-pattern tightening sequence in 3 stages (30%, 70%, and 100% of final torque).
Temperature Considerations: Allow for thermal expansion by reducing torque by 1% per 10°C above 25°C for steel fasteners.
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