Square Head Bolts M4 M5 M6 M8 M10 M12 — A2 304 Stainless Steel, Multiple Lengths

A general rule is to select a bolt length equal to the thickness of the material being fastened plus 1–1.5× the thread diameter for nut engagement. For example, joining two 10mm plates with an M6 bolt typically calls for a length of 25–30mm (≈1–1.2"). Lengths are measured from under the head to the tip of the shank. Always confirm clearance on the nut side before ordering.

A2 (304) stainless steel typically offers a tensile strength of around 500–700 MPa depending on diameter and manufacturing tolerances. These bolts are suitable for general-purpose structural and mechanical applications. They are not rated for high-tensile or safety-critical load-bearing joints — for those applications, consult an engineer and consider grade 8.8 or 10.9 alloy steel fasteners.

Yes. A2 304 stainless steel provides good corrosion resistance in most outdoor environments, including light coastal exposure. For highly aggressive marine or chloride-rich environments, A4 316 stainless steel is generally recommended. These bolts are well-suited for garden structures, outdoor furniture, pergolas, and general exterior applications without additional coating.

These bolts use standard ISO metric coarse threads throughout the M4–M12 range. Compatible with standard metric hex nuts, square nuts, flange nuts, and threaded inserts of the corresponding size. Typical coarse pitches: M4 = 0.7mm, M5 = 0.8mm, M6 = 1.0mm, M8 = 1.25mm, M10 = 1.5mm, M12 = 1.75mm. Always verify pitch compatibility if mixing fasteners from different sources.

Square head bolts are driven with an open-end wrench, adjustable wrench, or box wrench sized to the bolt head. They do not have a driver recess (no hex socket, Phillips, or Torx). The square head provides excellent grip and is less prone to rounding than hex heads when using adjustable tools — a key advantage in field assembly or when working with worn tools.

In many cases, yes. The square head profile is designed to slide into standard T-slot aluminum extrusion channels, allowing the bolt to be positioned without a separate T-nut. However, fit depends on the specific extrusion slot width and head dimensions. Verify the head width against your extrusion slot specification before ordering in bulk. Contact us if you need head dimension details for a specific size.

For a single repair or prototype, the 1-piece option lets you test fit before committing. For small projects or when you need a few spares, the 5-piece pack offers a better per-unit value. For production runs, recurring maintenance, or stocking a workshop, the 10-piece pack provides the lowest per-unit cost. All quantities ship from our US warehouse.