Phillips Flat Head Machine Screws M2.3 to M6 — Carbon Steel, Stainless & Brass, 7 Finishes

For countersunk flat head screws, the length is measured from the top of the head to the tip of the threads (total length including the head). Select a length so that the threaded portion engages at least 1.5–2 times the thread diameter in the mating material. For example, an M3 flat head screw fastening a 2mm panel into a 6mm aluminum block would typically use an M3 x 8mm screw: 2mm for the panel plus at least 4.5mm of thread engagement. For through-hole applications with a nut, the screw should extend 2–3 full threads past the nut face. In inches: M3 x 8mm is approximately 5/16"; M5 x 20mm is approximately 25/32"; M6 x 25mm is approximately 1".

A flat head (countersunk) screw has a tapered underside that seats flush with the surface when installed in a countersunk hole, leaving no protrusion above the material. A pan head screw has a rounded top and a flat underside that sits on top of the surface. Flat head screws are used when a flush or recessed finish is required — such as in furniture, electronics enclosures, and structural panels. Pan head screws are used when a flush finish is not required and the raised head provides a larger bearing surface. If your application does not have a countersunk hole, use a pan head or button head screw instead.

It depends on the finish selected. Stainless Steel offers good general corrosion resistance for outdoor and mildly humid environments. Carbon Steel with zinc plating (Black Zinc, White Zinc, Blue-White Zinc) provides moderate corrosion protection for indoor or sheltered use. Bright Chrome and Bright Nickel finishes are primarily decorative with moderate indoor corrosion resistance. Brass / Bright Nickel offers good corrosion resistance in non-marine environments and is commonly used in decorative and electrical applications. For marine or highly corrosive environments, stainless steel is generally the better choice.

All sizes use ISO metric coarse pitch threading: M2.3 (0.4mm pitch), M2.5 (0.45mm pitch), M3 (0.5mm pitch), M5 (0.8mm pitch), M6 (1.0mm pitch). These screws are compatible with standard metric nuts, threaded inserts, and tapped holes of the corresponding size and pitch. They are not compatible with UNC or UNF inch-standard threads. If you are tapping your own holes, use the corresponding metric tap for each size. M2.3 is a less common size primarily used in miniature electronics and optical instruments — verify your existing hardware before ordering.

Phillips flat head machine screws typically use an 82° or 90° countersink angle depending on the manufacturing standard. DIN 965 (the most common metric standard for flat head machine screws) specifies a 90° countersink angle. Some US-style metric screws use 82°. Contact us to confirm the countersink angle for your specific variant before machining countersunk holes, especially for precision applications where a flush fit is critical. Using the wrong countersink angle will result in the head either sitting proud of the surface or sinking below it.

Carbon steel flat head machine screws are generally rated to property class 4.8 or higher, with tensile strengths typically ranging from 420 MPa to 800 MPa depending on the specific grade. Stainless steel variants are generally rated to A2-70, with a tensile strength of approximately 700 MPa. Brass screws are generally softer, with tensile strengths typically in the range of 300–500 MPa, and are suited for light-duty fastening in decorative, electrical, and non-structural applications. Contact us to confirm the exact property class if your application has specific strength requirements.

Brass / Bright Nickel flat head screws are a good choice when you need non-magnetic fasteners, good electrical conductivity, or a warm gold-toned decorative appearance with a silver nickel finish. They are commonly used in electrical panels, musical instruments, decorative woodworking, and applications where galvanic corrosion between dissimilar metals is a concern. Brass is softer than carbon or stainless steel, so it is not suitable for high-load structural applications. The Bright Nickel plating adds a silver-toned decorative finish over the brass base, making these screws visually distinct from standard carbon steel nickel-plated variants.