M4 & M6 Phillips Pan Head Machine Screws with Hex Nuts | A2 304 Stainless Steel, 5mm–120mm

Measure the total thickness of all materials being clamped together, then add the nut height plus at least 1–2 thread pitches of protrusion beyond the nut for a secure grip. For M4 bolts (0.7mm pitch), the nut is typically about 3.2mm tall; for M6 (1.0mm pitch), approximately 5mm. For example, clamping two 5mm aluminum plates with an M4 bolt generally calls for an M4 × 14mm or 16mm bolt. When in doubt, size up — excess thread can be managed with a washer.

A2 is the ISO designation for 304 austenitic stainless steel, containing approximately 18% chromium and 8% nickel. It provides good corrosion resistance in most indoor and outdoor environments, resists rust and staining, and is generally non-magnetic in its annealed state. It is the most widely used stainless steel grade for general-purpose fasteners and is a significant improvement over zinc-plated carbon steel in humid or wet conditions.

Yes. A2 304 stainless steel provides good corrosion resistance and is generally suitable for outdoor use in most climates, including light marine environments. For prolonged saltwater or highly corrosive coastal exposure, A4 316 stainless steel is typically recommended for superior resistance.

Yes. Each set includes a matching bolt and hex nut with the same ISO metric coarse thread standard: M4 × 0.7mm pitch and M6 × 1.0mm pitch. The nuts are standard ISO hex nuts compatible with the corresponding bolt diameter. They are not compatible with UNC or UNF inch-standard threads.

A2 stainless steel fasteners typically meet ISO property class A2-70, with a minimum tensile strength of 700 MPa for the bolt. The matching hex nuts are generally rated to the same property class. They are suitable for general-purpose and light-to-medium structural fastening. For high-load or critical structural applications, consult the specific grade markings or contact us to confirm.

These screws use a Phillips (PH) cross-head drive. For M4 screws, a PH2 (Phillips #2) bit is typically correct. For M6 screws, a PH2 or PH3 bit is generally used. The hex nut can be tightened with a standard metric open-end or combination wrench: 7mm AF for M4 nuts, 10mm AF for M6 nuts. Using the correct bit size reduces cam-out and head damage during installation.

Washers are not included but are generally recommended when fastening into soft materials such as wood, plastic, or thin aluminum sheet, to distribute clamping load and prevent the nut from pulling through. For metal-to-metal connections with adequate material thickness, washers are typically optional. Flat washers in M4 and M6 sizes are widely available and compatible with these fasteners.