Square plate washers are heavy-duty, thick steel fasteners featuring a large, square external profile and a central round or square clearance hole.
They are engineered to distribute heavy fastening loads across a significantly wider surface area than standard round washers. They are predominantly utilized in structural timber joints, heavy steel framing, civil engineering, and concrete anchoring systems.
Core Functions
- Preventing Timber Crushing: In timber-to-timber and timber-to-steel connections, they distribute the immense clamping force of high-tensile bolts, preventing the bolt head or nut from tearing into and crushing soft wood fibres.
- Bridging Oversized Holes: Their large surface area spans wide, slotted, or poorly aligned clearance holes in steel plates or concrete foundations without slipping through.
- Maximising Friction and Joint Rigidity: The square edges grip larger surface boundaries, preventing the washer from spinning, warping, or dishing under extreme high-torque clamping.
Key Manufacturing Standards
- BS 4320 Form G: A classic British standard specifying large, thick round and square washers often paired with heavy structural wood bolts.
- DIN 436: The standard European specification for square washers explicitly intended for use in timber construction, outlining precise thickness-to-width ratios.
Common Material and Coating Grades
- Bright Zinc Plated (BZP) Steel: Provides light corrosion protection, ideal for dry, indoor structural framing and internal carpentry.
- Hot Dip Galvanised (HDV) Carbon Steel: Features a thick, rugged zinc coating offering premium atmospheric corrosion protection, essential for outdoor structural timber frames, fencing, roofing, and marine environments.
Stainless Steel (A2/304 or A4/316): Used where extreme environmental resilience is required, such as coastal construction, water treatment facilities, or chemical processing plants.
