Phillips Countersunk Machine Screws 304 A2 Stainless Steel M4 M5 M6 | Flat Head Metric Bolts

For countersunk (flat head) screws, the listed length is the total length of the screw including the head. Measure the full thickness of the material you are fastening, then add the depth of engagement needed in the receiving thread. For example, M4×16mm (≈5/8") is typically used for 10–12mm material with a tapped hole or nut. When in doubt, choose a length that allows at least 1.5× the thread diameter of engagement in the mating part.

304 (A2) stainless steel machine screws generally have a tensile strength of approximately 500–700 MPa, equivalent to ISO 3506 property class A2-50 or A2-70. They are suitable for light-to-medium structural applications. For heavy-load or high-vibration environments, consider A4 (316) stainless or alloy steel alternatives.

Yes. 304 stainless steel offers good corrosion resistance and is suitable for most outdoor and mildly humid environments — it resists rust and oxidation well under typical weather conditions. For marine or chloride-heavy environments (saltwater, pool surrounds), 316 (A4) stainless steel is generally recommended for better long-term performance.

Yes. These screws use ISO metric coarse thread (M4 × 0.7 mm, M5 × 0.8 mm, M6 × 1.0 mm) and are fully compatible with any standard metric M4, M5, or M6 nut, threaded insert, or tapped hole following the ISO 68-1 thread form. They are not compatible with UNC/UNF inch-standard fasteners.

M4 and M5 screws typically use a PH2 (Phillips #2) driver bit. M6 screws also generally accept PH2, though some M6 variants may fit a PH3. Always verify the recess size before driving to avoid cam-out and head damage. Using a correctly sized bit and applying firm downward pressure reduces the risk of stripping.

Choose based on the tapped hole or nut size already in your assembly:

• M4 (≈5/32") — Electronics enclosures, thin sheet metal, small fixtures, RC and hobby hardware.
• M5 (≈3/16") — Machinery brackets, aluminum extrusion frames, furniture hardware, general fabrication.
• M6 (≈1/4") — Heavier structural connections, automotive trim, industrial equipment, thicker panels.

If designing from scratch, M5 is a versatile middle-ground choice for most DIY and light industrial applications.

Yes — countersunk flat head screws are designed to sit flush with or slightly below the workpiece surface when used with a properly countersunk hole. The countersink angle for these metric screws is 90°. Use a 90° countersink bit matched to the screw diameter to prepare the hole before driving for a clean, flush result.

These are machine screws designed for use with a pre-tapped hole, threaded insert, or nut — they are not self-tapping. They work well in aluminum, steel, and hard plastics with a properly tapped M4/M5/M6 hole. For wood or soft materials, a threaded insert is generally recommended to provide a durable mating thread. Contact us if you need guidance on the right fastener for your specific material.