304 Stainless Steel Thick Rod Half-tooth Hexagon Screw Cylindrical Cup Head Bolt
Release time：2020-01-16 18:44 Browse：
304 Stainless Steel Composition: Composed of 18% chromium and 8% nickel with a carbon content of ≤0.08%. This composition endows it with excellent corrosion resistance, making it suitable for humid, mildly corrosive environments, such as coastal areas or food processing plants.
Strength Characteristics: Boasting a tensile strength of at least 520 MPa and a yield strength of 205 MPa in the annealed state. It also offers an elongation of ≥40%, ensuring ductility and preventing brittleness under stress, ideal for applications where durability matters.
Available Sizes: Offered in metric diameters of M5, M6, M8, M10, and M12, with extended lengths ranging from 30 to 300 millimeters. These longer lengths are designed to meet the demands of deep - mounting applications, like securing thick structural components.
Half - Threaded Design: Approximately 50% of the screw's total length is threaded. For instance, on an M10×100mm screw, around 50mm of the length features threads. The threads follow the Metric coarse standard (ISO 68 - 1), with pitches varying by size, such as M5×0.8 and M12×1.75. The thread accuracy adheres to the 6g tolerance for external threads, ensuring a proper fit with 6H nuts.
Cylindrical Cup Head (Hex Socket): Conforms to ISO 4762 standards. The head diameter is 1.5 times the screw diameter (e.g., an M8 screw has a 13mm head diameter), and the head height is 0.7 times the diameter (e.g., 6.5mm for M8). The internal hex drive size is determined by ISO 273 (e.g., 6mm key size for M8), allowing for high - torque application during installation.
Thick Rod Shank: The unthreaded grip section has a diameter close to the nominal screw diameter. This design minimizes stress concentration in shear - loaded joints, effectively transferring loads through the solid rod part of the screw, enhancing the joint's strength. The surface of the shank has a mill finish with a roughness of Ra ≤12.5μm, and can be optionally polished for specific requirements.
Enhanced Stress Management: By having a solid unthreaded shank, the screw can more efficiently transfer loads in shear - critical applications, such as connecting beams. This design reduces the risk of failure at the threaded section under shear forces, increasing the overall structural integrity of the assembly.
Assembly Efficiency: For long screws, the half - threaded design reduces the time required for threading during the manufacturing process. Additionally, it helps prevent thread damage when inserting the screw into deep holes, making the installation process smoother and more reliable.
Standard Passivation: Treated with passivation according to ASTM A967 standards. This process forms a protective Cr₂O₃ layer on the surface, providing over 500 hours of salt spray resistance. This ensures the screw maintains its integrity in outdoor or damp indoor environments.
Optional Coatings: For specialized applications, additional coatings are available. PTFE coating can be applied to reduce friction, which is useful in moving parts or where low - torque operation is required. Black oxide coating can be used for applications that demand an anti - glare surface, such as in certain aviation or optical equipment.
Heavy Machinery: Ideal for mounting large motors, industrial presses, and the frames of heavy - duty equipment. The high strength and corrosion resistance of 304 stainless steel ensure the screws can withstand the vibrations and stresses associated with such machinery.
Construction and Infrastructure: Used for deep anchoring in concrete structures and for connecting steel components in construction projects, like bridge bearings. Their extended length and robust design make them suitable for providing secure connections in large - scale infrastructure builds.
Marine and Offshore: Due to their corrosion - resistant properties, these screws are well - suited for shipbuilding and offshore platform construction. They can endure the harsh marine environment, including exposure to saltwater and humidity.
Torque Recommendations: Based on ISO 898 - 1 standards, torque values vary by screw size. For dry installation, an M5 screw requires a torque of 4 - 5 Nm, while an M12 screw needs 35 - 40 Nm. When lubricated, the torque values decrease slightly, with M5 at 3 - 4 Nm and M12 at 28 - 32 Nm.
Tooling: To achieve the required torque, use hex socket drivers. The key size is approximately 0.5 times the screw diameter; for example, a 6mm key is needed for an M10 screw. This ensures a proper and secure fit during installation.
Testing Procedures: Rigorous quality control measures are in place, including thread Go/No - Go gauging to ensure proper thread formation. Head dimensions are also checked using calipers, with a tolerance of ±0.1mm. Random samples from each batch (usually 5 pieces) undergo tensile testing to confirm they can withstand a minimum of 520 MPa.
Compliance and Documentation: The screws comply with RoHS and REACH regulations, ensuring they are free from hazardous substances. They also carry CE marking for structural use according to EN 1090. Material test reports (MTRs) are available upon request, providing detailed information about the material's composition and mechanical properties.
Bulk Packaging: For storage and transportation, M5 - M8 screws are packed 500 pieces per carton, while M10 - M12 screws are packed 200 pieces per carton. Each carton is equipped with moisture - absorbing desiccant to protect the screws from rust during transit and storage.
Lead Times: Standard - sized screws can be shipped within 24 - 48 hours. For custom - length screws, especially those longer than 150mm, the lead time is typically 5 - 7 working days, ensuring a balance between customization and timely delivery.
Compared to Full - Threaded Screws: In shear - loaded applications, these half - threaded screws demonstrate approximately 20% higher shear strength due to the solid shank design. Testing according to EN 1993 - 1 - 8 has proven their superiority in such scenarios.
Compared to Carbon Steel Screws: Without additional plating, 304 stainless steel screws offer three times better corrosion resistance in outdoor environments. This makes them a more reliable and low - maintenance choice for long - term use in exposed settings.
