Stainless Steel Expansion Bolts for Marble & Stone — M6 M8 Heavy Duty Anchor Bolts

A general rule is to select a bolt length that allows at least 1.5× the bolt diameter of embedment depth into the base material. For M6 bolts, that typically means at least 9mm (≈3/8") of anchor engagement; for M8, at least 12mm (≈1/2"). For example, if your marble slab is 20mm (≈13/16") thick and you need to anchor into a concrete substrate, an M6×40mm bolt generally provides sufficient grip. When in doubt, choose the next longer size.

Load capacity depends on the base material, embedment depth, and bolt grade. In solid concrete, M6 expansion anchors typically support 0.8–1.5 kN (180–340 lbf) in tension and M8 anchors typically support 1.5–2.5 kN (340–560 lbf). In softer stone such as marble or limestone, values are generally lower. Always consult a structural engineer for load-critical applications.

The 304 stainless steel variants offer good corrosion resistance and are generally suitable for outdoor, humid, and mildly corrosive environments such as patios, pool surrounds, and exterior stone cladding. The 201 stainless steel variants are better suited for indoor or sheltered applications. For marine or highly chloride-rich environments, 316 stainless steel is typically recommended instead.

These bolts use standard metric coarse threads (ISO 68-1). M6 has a standard pitch of 1.0mm and M8 has a standard pitch of 1.25mm. They are compatible with standard metric nuts and washers. They are not compatible with UNC/UNF imperial thread fasteners.

304 stainless steel contains a higher nickel content (typically 8–10.5%) which gives it superior corrosion resistance, making it the preferred choice for outdoor, humid, or food-adjacent applications. 201 stainless steel has a lower nickel content and is generally more economical, making it a practical choice for dry indoor installations where maximum corrosion resistance is not required.

For wall-mounted marble panels, anchors are typically spaced 300–600mm (12"–24") apart along each edge, depending on panel weight and size. A standard 600×600mm (24"×24") tile or panel generally requires 4–6 anchor points. We offer packs from 5 to 100 pieces so you can order exactly what your project requires.

These anchors are designed primarily for natural stone (marble, granite, limestone) and concrete substrates. Ceramic tile and porcelain are generally too brittle and thin for mechanical expansion anchors — the expansion force can crack the tile. For ceramic or porcelain, adhesive anchors or through-bolt systems are typically recommended instead.