M3 Phillips Pan Head Machine Screws — 3 to 20mm, Carbon Steel & Stainless, 7 Finishes

Select a length so that at least 1.5–2 times the thread diameter (4.5–6mm for M3) engages in the mating material. For example, if your panel is 3mm (about 1/8") thick, an M3 x 6mm or M3 x 8mm screw is typically appropriate. For through-hole fastening with a nut, the screw should extend at least 2–3 full threads past the nut face. The 3mm and 4mm lengths are generally suited for very thin panels or PCB standoff applications where minimal thread engagement is needed.

The D= value specifies the outer diameter of the pan head at its widest point. For example, “M3 x 6mm D=5.5” means the screw is 6mm long with a pan head that is 5.5mm in outer diameter. Standard M3 pan head screws may have slightly different head diameters depending on the manufacturing standard (ISO 7045, DIN 7985, etc.). If your application has a specific clearance hole or recess for the head, select the D= variant that matches your requirement. If no D= is specified in the variant name, the head diameter follows the standard for that size.

The “± Slot” designation means this variant has both a Phillips cross recess and a flathead slot cut into the head, making it a dual-drive screw. It can be driven with either a Phillips (PH1) screwdriver or a standard flathead screwdriver. This is useful in field repair situations where only one driver type is available, or in applications where a flathead driver provides better torque control in soft or delicate materials. The dual-drive feature does not reduce the screw’s load capacity.

Stainless Steel Blackening (black oxide on stainless) is a chemical conversion coating that gives stainless steel a dark, matte black appearance while retaining the corrosion resistance of the underlying stainless steel. It is commonly used in tactical equipment, optical instruments, camera rigs, and dark-finish assemblies where a non-reflective, corrosion-resistant fastener is needed. The black finish is generally more durable than paint but may show wear on high-contact surfaces over time. It does not significantly affect the screw’s dimensional tolerances.

It depends on the finish selected. Stainless Steel and Stainless Steel Blackening variants offer good general corrosion resistance and are suitable for most outdoor and mildly humid environments. Carbon steel variants with zinc plating (black, white, blue, or blue-white) provide moderate corrosion protection for indoor or sheltered use. Bright nickel-plated carbon steel is primarily decorative with moderate indoor corrosion resistance. For marine or highly corrosive environments, stainless steel is generally the better choice.

M3 uses the ISO metric thread standard with a standard coarse pitch of 0.5mm. These screws are compatible with standard M3 metric nuts, threaded inserts, and tapped holes. They are not compatible with UNC or UNF inch-standard threads. If you are tapping your own holes, use an M3 x 0.5 tap. If you are unsure whether your existing hardware is M3 metric or an inch equivalent, measure the thread diameter and pitch with a thread gauge before ordering.

Carbon steel M3 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. For small-diameter screws like M3, actual load capacity is limited by the thread cross-section and is suitable for light-duty fastening in electronics, enclosures, and precision instruments. Contact us to confirm the exact property class if your application has specific strength requirements.