M3–M6 Flanged Button Head Screws, A2 Stainless Steel Allen Socket Machine Bolts

A general rule: the screw length should be approximately 2–3× the thread diameter for most clamping applications. For example, an M4 screw typically works well at 10–16mm (3/8"–5/8") for sheet metal or panel fastening. Always measure the material thickness and add enough thread engagement — generally at least 1.5× the diameter into the receiving material. For through-bolting with a nut, the length should equal material thickness plus nut height plus a few threads of protrusion.

A2 stainless steel (ISO 3506 property class 70) generally provides a tensile strength of approximately 700 MPa. Recommended tightening torques typically range from about 0.5 Nm for M3 up to 5 Nm for M6, though exact values depend on lubrication, mating material, and application. Consult a qualified engineer for safety-critical or load-bearing assemblies.

A2 stainless steel offers good corrosion resistance and is generally suitable for outdoor, humid, and mildly corrosive environments. For marine or chloride-heavy environments (saltwater, coastal areas), A4 (316) stainless is typically recommended for long-term performance. These screws are not coated or plated — the corrosion resistance comes from the stainless alloy itself.

These screws use standard ISO metric coarse threads (M3, M4, M5, M6). They are compatible with standard metric nuts, heat-set threaded inserts, T-nuts for aluminum extrusions, and tapped holes following ISO 68-1 thread profiles. They are not compatible with UNC or UNF inch-standard threads.

Standard ISO hex socket sizes apply: M3 uses a 2mm hex key, M4 uses 2.5mm, M5 uses 3mm, and M6 uses 4mm. These are standard sizes found in most metric Allen wrench sets and hex bit driver kits.

The integrated flange acts as a built-in washer, distributing clamping load over a wider bearing area than a standard button head. This reduces the risk of surface damage on softer materials (plastic, aluminum, wood), eliminates the need for a separate washer in most applications, and provides a cleaner finished appearance — making these screws popular in electronics enclosures, furniture assembly, and visible mechanical assemblies.

Yes. These screws are commonly used with aluminum extrusions (including 2020/3030/4040 profiles), plastic panels, and hardwood. For softer materials like plastic or wood, the flanged head helps prevent pull-through by spreading the load. Always pre-drill a clearance hole or use appropriate threaded inserts for best results in non-metallic materials.

If you are prototyping or need a specific size for a one-off repair, the 5 or 10-piece packs let you try the size without committing to a large quantity. For ongoing projects — such as building a 3D printer, assembling aluminum frame panels, or stocking a workshop — the 50, 100, or 200-piece packs generally offer a lower per-unit cost and reduce the chance of running short mid-project.