Flat Square Plate Washers 304/316 Stainless Steel Square Washers Thick Stamped Metal Spacers for Construction Railing & Fastening

Our square flat washers (also known as square washers, square metal spacers) are manufactured from AISI 304/316 stainless steel or Q235 carbon steel, with strength grades covering stainless steel A2 (304) / A4 (316) and carbon steel grades 4.8 / 8.8. The products strictly comply with GB/T 97.1, JGJ 130, DIN 436, ISO 7091 and other standards, available in a range of side length × thickness dimensions (e.g., sizes to suit M4‑M24) with custom thickening or non‑standard sizes offered. The square shape provides a larger contact area and greater rotation resistance on square tubes, channels, wood and irregular surfaces compared to round washers – particularly suited for building curtain wall frames, railing post connections, outdoor balustrade bases, and heavy equipment assembly. The precisely centered hole and smooth, burr‑free edges allow easy installation: simply slide onto a bolt or screw and tighten with a nut to distribute pressure and prevent workpiece surface damage. The 316 stainless steel variant offers salt spray resistance ≥720h, ideal for coastal bridges, ship decks and other corrosive environments.

Square flat washers are produced using a high‑precision progressive die continuous stamping process. Raw coil stock is leveled and fed into a high‑speed press (speed ≥120 strokes/min), where a single die set performs compound blanking in sequence: pre‑punch pilot holes, flatten the surface, punch the inner hole, and cut the outer square – ensuring inner‑outer concentricity ≤0.1mm and vertical edges without die roll. For thicker specifications (≥3mm), a multi‑station cold heading + fine blanking combined process is used to avoid shear fractures. After stamping, parts are tumble deburred or magnetic finished to remove sharp edges, achieving a smooth, safe‑to‑touch finish. Carbon steel versions can undergo mesh‑belt bright heat treatment to relieve internal stress and ensure uniform hardness. Surface finishing: carbon steel is electro‑galvanized (8‑12μm, blue/white or yellow zinc) or hot‑dip galvanized (≥50μm); stainless steel is electropolished or passivated to enhance passive film density. Every batch is 100% inspected for inner hole and outer dimensions using go/no‑go gauges, with sample testing for salt spray (≥720h for stainless steel, ≥72h for electro‑galvanized) and hardness.

As a source factory, we are committed to breaking down the information barriers of traditional trade. From mill certificates for raw materials to hardness grades (covering Grade 4.8 to Grade 12.9, as well as A2-70 and A4-80 marine-grade stainless steel), all test data is traceable. We support full-chain customization: dimensionally, we can adjust thread length and head thickness according to drawings; functionally, we can combine processes like sandblasting, electrophoretic coating (e-coating) , or chrome plating. Whether you need British Standard (BS) fasteners or require a special colored anodized finish, we offer small-batch sampling. This ensures that when you purchase fasteners from us, you not only receive high-quality products but also full transparency and control over the entire process, from material selection to packaging.

304/316 stainless steel square washers, certified to multiple standards including GB, DIN, and ISO. The square structure increases the contact surface, preventing rotation and loosening, and perfectly fitting square pipes and guardrail bases. A4 grade salt spray resistance ≥720h, the first choice for outdoor marine and building curtain walls.