M10 M12 Square Head Bolts 304 Stainless Steel — Metric Square Head Screws

A general rule is to select a bolt length equal to the thickness of the material being fastened plus 1–1.5× the bolt diameter for adequate thread engagement. For example, fastening a 20mm (≈3/4") plate with an M10 bolt typically calls for a 30–40mm length. Always verify clearance on the nut side before ordering. If you are unsure, contact us with your application details.

304 (A2) stainless steel bolts generally have a tensile strength of approximately 500–700 MPa depending on diameter and manufacturing standard. They are suitable for moderate-load structural and mechanical applications. For high-stress or safety-critical joints, consult a structural engineer and consider A4-80 (316 SS) grade fasteners.

304 stainless steel offers good corrosion resistance in most outdoor environments and is commonly used in construction, landscaping, and light marine applications. However, in high-chloride or direct saltwater environments, 316 (A4) stainless steel is generally recommended for longer service life. For covered outdoor structures, pergolas, and decks, 304 SS typically performs well.

Yes. These bolts use ISO metric coarse threads — M10 at 1.5mm pitch and M12 at 1.75mm pitch. They are fully compatible with standard metric hex nuts, square nuts, and flanged nuts of the corresponding size available at any hardware store. They are not compatible with UNC or UNF inch-thread hardware.

Square head bolts are typically driven with an adjustable wrench, open-end wrench, or pipe wrench. M10 square heads are generally approximately 14–17mm across flats, and M12 square heads are typically around 17–19mm across flats. Contact us to confirm the exact head dimensions for your specific variant before selecting tooling.

Yes — square head bolts are a traditional choice for timber framing, post-and-beam construction, and heavy wood joinery. The square head resists rotation when seated in a square countersink or against a washer in wood, making installation with a single wrench straightforward. The 304 stainless steel material also resists the tannin-based corrosion that can affect zinc-plated fasteners in treated lumber.

Quantity options are listed in the variant selector above and vary by diameter and length — typically available as 1, 3, 5, 8, 10, 15, 20, 25, or 30 pieces per order. Larger quantities are priced at a lower per-piece cost, making bulk orders cost-effective for contractors and fabrication shops stocking up for a project.