As a general rule, the engaged thread length should be at least 1.5× the screw diameter for steel-into-steel joints. For example, an M6 screw threading into steel should engage at least 9mm (≈3/8"). Always measure the material thickness and add clearance for the head height (typically 1.65–3.5mm depending on size). Quick inch conversions: 10mm ≈ 3/8", 20mm ≈ 13/16", 25mm ≈ 1", 30mm ≈ 1-3/16", 50mm ≈ 2".

Grade 12.9 alloy steel screws have a minimum tensile strength of 1220 MPa (≈177,000 psi) and a proof load of typically 1100 MPa. This makes them among the strongest standard metric fastener grades, suitable for high-stress mechanical assemblies, automotive components, and precision machinery where fastener failure is not acceptable.

Grade 12.9 alloy steel is generally not inherently corrosion-resistant. For outdoor, humid, or chemically exposed environments, we recommend applying a corrosion-inhibiting coating or selecting stainless steel alternatives. If these must be used outdoors, a zinc-nickel or black oxide treatment can extend service life. Contact us to confirm coating availability for your order.

These screws use ISO metric coarse threads: M3×0.5, M4×0.7, M5×0.8, M6×1.0, and M8×1.25. They are compatible with standard metric nuts, threaded inserts, and tapped holes following ISO 68-1 thread profiles. They are not compatible with UNC or UNF inch-standard threads.

The required hex key size follows the metric standard: M3 uses a 2mm key, M4 uses 2.5mm, M5 uses 3mm, M6 uses 4mm, and M8 uses 5mm. Always verify with the actual fastener before applying full torque to avoid rounding the socket.

Button pan head screws have a wider, lower-profile dome head compared to standard socket cap heads. This distributes clamping load over a larger surface area, reduces the risk of pull-through in softer materials like aluminum or plastic panels, and provides a cleaner, more finished appearance in visible assemblies such as enclosures, consumer electronics, and display fixtures.

Yes, button pan head screws are commonly used in aluminum extrusion builds and hard plastic assemblies. The wider head distributes load and reduces surface damage. For softer plastics, consider adding a washer to further spread the clamping force. Avoid over-torquing — Grade 12.9 screws can strip threads in softer base materials if excessive torque is applied.