A2 Stainless Steel Mushroom Head Slotted Machine Screws — M2 to M8, Multiple Lengths

Generally, the screw length should equal the thickness of the material being fastened plus enough thread engagement in the receiving part — typically 1.5× the screw diameter. For example, an M4 screw fastening 6mm of material into a threaded hole would typically need at least 12mm total length. As a quick inch reference: 10mm ≈ 3/8", 25mm ≈ 1", 50mm ≈ 2".

A2 stainless steel (also known as 304 stainless) generally has a tensile strength of around 500–700 MPa depending on the grade and processing. These screws are well-suited for light-to-medium duty fastening applications. For heavy structural loads, consult an engineer or consider A4 (316) or high-tensile steel alternatives.

A2 stainless steel offers good corrosion resistance and is suitable for most outdoor environments including light coastal exposure. For prolonged saltwater or marine immersion, A4 (316) stainless is generally recommended. In typical outdoor DIY, garden, or light industrial settings, A2 performs well without rusting or staining.

These are metric machine screws following the ISO 68-1 thread standard with standard coarse pitch (e.g., M3 = 0.5mm pitch, M4 = 0.7mm pitch, M5 = 0.8mm pitch, M6 = 1.0mm pitch, M8 = 1.25mm pitch). They are compatible with standard metric nuts, threaded inserts, and tapped holes of the corresponding size. They are not compatible with UNC or UNF inch-standard threads.

These screws have a slotted (straight) drive and require a flat-head screwdriver of the appropriate blade width for the screw size. For M2–M3, a small precision flat-head is typically used; for M4–M8, a standard flat-head screwdriver works well. Avoid power-driving at high torque to prevent cam-out on the slotted head.

The mushroom or domed head provides a wider bearing surface than a pan head, distributing clamping force over a larger area — useful when fastening softer materials or thin panels. The low, rounded profile also gives a cleaner finished appearance compared to a raised hex head, making it popular in electronics enclosures, furniture, and decorative fixtures.

These are machine screws designed for use with pre-tapped holes, threaded inserts, or matching nuts — not for self-tapping into wood or plastic. For wood, wood screws are more appropriate. For plastic, a brass or stainless threaded insert installed first will give the best results with these machine screws.