DIN6921 Hex Flange Bolt A4-70 | Serrated Flange Screw
TheDIN 6921 hex flange bolt — also referred to as a flange screworhexagon head bolt with flange — integrates a circular formed washer-flange into the underside of the bolt head. Unlike standard hex bolts that require a separate flat washer to distribute clamping force, the flange bolt delivers immediate, reliable bearing surface contact with a single component. The built-in flange spreads the clamp load over a larger area, protecting soft substrate materials from deformation and eliminating the assembly step, inventory line item, and potential mismatch of independent washers. The flange face is available in plain (non-serrated) for general use and serrated flange bolt for applications requiring anti-rotation friction and resistance to vibration loosening.
In marine engine rooms and piping systems, DIN 6921 flange bolts are widely used where speed of assembly and joint integrity are both critical — pipe flange connections, pump and motor mounting brackets, heat exchanger flange joints, valve body bolting, and compressed air manifold covers. The A4-70 hex flange bolt (316 stainless steel) provides full seawater corrosion resistance for direct bilge-area and salt-laden atmosphere exposure, while Grade 8.8and10.9 carbon steel flange bolts with zinc, Dacromet, or Geomet coatings deliver high clamping strength at a lower cost for protected engine room installations. The one-piece design is particularly valued in confined machinery compartments where fumbling with a separate flat washer during installation wastes time and risks dropped washers into inaccessible bilge spaces.
Ourhex flange bolts are precision cold-forged to DIN 6921andISO 4161 dimensional standards, with full-thread and partial-thread configurations available in metric sizes M5 through M24. Stainless steel grades A2-70 and A4-80 are passivated after forming; carbon steel grades 8.8, 10.9, and 12.9 are heat-treated per ISO 898-1. Serrated flange bolts are supplied with 6 to 12 radial serrations under the flange face to create mechanical interlock with the mating surface when torqued. Material certification to EN 10204 3.1 and class society (IACS) documentation are standard deliverables for marine project orders.
| Product Name | DIN 6921 Hex Flange Bolt / Hexagon Head Flange Screw / integrated washer bolt |
| Standard | DIN 6921 / ISO 4161 / ISO 4162 |
| Head Type | Hexagon head with integrated flange (plain or serrated face) |
| Size Range | M5 – M24 |
| Thread | Metric coarse, full-thread / partial-thread options |
| Material | A2-70 / A4-70 / A4-80 SS / Grade 8.8 / 10.9 / 12.9 Carbon Steel |
| Flange Type | Plain (non-serrated) / Serrated (6-12 radial ribs) |
| Finish | Passivated (SS) / Zinc Plated / Dacromet / Geomet / HDG |
| Key Benefit | Eliminates separate flat washer — larger bearing area, faster assembly |
| Applications | Pipe flange, pump bracket, heat exchanger, valve body, engine mount |
| Certification | EN 10204 3.1, IACS (LR, DNV, BV, ABS) |
| Packing | Carton / Pallet / Custom labeling |
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