M3 Knurled Thumb Screws A2 Stainless Steel Flat Head Thumbscrew Bolts 6mm to 20mm

Generally, the screw length should equal the thickness of the material being fastened plus the required thread engagement depth. For M3 screws, a thread engagement of at least 3–4mm is typically recommended. For example, if your panel is 3mm thick and you need 3mm of thread engagement, a 6mm (≈1/4") screw is usually the right choice. Always measure your specific application before ordering.

A2 stainless steel generally has a tensile strength of around 500–700 MPa depending on the specific manufacturing process. For M3 thumb screws used in hand-tightened applications — such as panel covers, enclosures, and light mechanical assemblies — this is typically more than adequate. For structural or high-vibration applications, consult a fastener engineer for exact torque and load specifications.

A2 stainless steel offers good corrosion resistance and is generally suitable for outdoor use in mild to moderate conditions. It resists rust and surface oxidation well in most weather. For highly corrosive environments — such as marine, coastal, or chemical exposure — A4 (316) stainless steel is typically the better choice. Contact us if you need guidance on material selection for your specific environment.

These screws use the standard M3 metric coarse thread at 0.5mm pitch, conforming to ISO 68-1. They are compatible with any M3-threaded hole, brass heat-set insert, or standard M3 nut that follows the same ISO metric thread standard — including those commonly used in 3D printer frames, electronics enclosures, and RC model chassis.

The knurled flat head is designed for hand-tightening without tools in most light-duty applications. The textured grip pattern allows for firm finger torque. Some variants in this style also include a flat-head screwdriver slot for additional torque when needed — please check the product images to confirm whether a drive slot is present on this specific listing.

These are commonly used in electronics enclosures, 3D printer frame panels, RC model chassis, DIY instrument panels, computer case modding, and any build where frequent tool-free access is needed. The flat head profile keeps them flush or near-flush with the surface, making them a clean solution for visible panels.

You can select your pack quantity directly on this page: 1, 2, 5, 10, 20, 50, or 100 pieces. Larger packs offer a lower per-unit cost, making them practical for bulk builds or keeping workshop stock on hand. For quantities beyond 100 pieces, contact us to discuss wholesale or custom order options.