Bolts · DIN 6921
DIN 6921 Flange Bolt
Accurate Fastners manufactures and supplies DIN 6921 hexagon flange bolts in stainless steel grades SS 304 and SS 316, covering diameters from M5 to M10 and lengths from 10 mm to 100 mm. Cold-forged to DIN 6921, these bolts are suited to assemblies where a wider bearing surface and external-hex drive are both required.
- Standard
- DIN 6921
- Grades
- 304 / 316
- Size
- M5 – M10
- Length
- 10 mm – 100 mm
Overview
What is the DIN 6921 Flange Bolt?
DIN 6921 is a German standard defining hexagon bolts with an integral flange beneath the head. The flange acts as a built-in washer, distributing the clamping load across a broader contact area without requiring a separate flat washer in the joint. This makes the fastener a common choice in production environments where parts counts and assembly steps are kept to a minimum.
The bolt features a full hexagonal head sitting above a wide, circular flange that is formed integrally during the cold-forging process. The underside of the flange is typically serrated or smooth depending on the variant, and the shank carries a standard metric thread. Drive is applied externally via a hex spanner or socket, which is straightforward to automate on assembly lines.
What distinguishes Accurate Fastners' DIN 6921 flange bolts is the cold-forging process used to produce them. Cold forging refines the grain structure of the stainless steel, generally improving mechanical consistency compared with machined alternatives. Sizes range from M5 to M10, with lengths from 10 mm to 100 mm, giving designers reasonable flexibility across light-to-medium structural and sheet-metal applications.
In Depth
Product description
Construction & Geometry
Each bolt is produced by cold forging, which forms the hexagonal head and integral flange in a single continuous process. The flange diameter is proportionally larger than the across-flats dimension of the hex head, creating a bearing shoulder that spreads load without added components. Metric threading runs along the shank in accordance with DIN 6921 profile requirements.
Available diameters span M5 through M10, and the length range of 10 mm to 100 mm accommodates a variety of panel thicknesses and joint depths. All dimensional proportions—head height, flange diameter, and thread engagement—follow the DIN 6921 specification, helping engineers maintain interchangeability when sourcing from multiple suppliers across a project lifecycle.
Functional Behaviour in an Assembly
In a bolted joint, the integrated flange contacts the workpiece surface as the bolt is tightened, bridging the function of a separate flat washer. This distributes the compressive stress over a greater area, which may reduce the risk of surface indentation in softer substrates such as aluminium extrusions or thin sheet steel used in enclosures and frames.
The external hex drive allows high torque input using standard tooling, and the wide flange provides a stable seating surface that can help resist loosening under vibration. In stainless steel, the absence of a separate washer also eliminates one potential site for crevice moisture retention, which is a practical consideration in wash-down or humid operating environments.
How It Differs from Similar Fasteners
A standard DIN 931 or DIN 933 hex bolt requires a separate flat washer to achieve comparable load distribution. The DIN 6921 flange bolt eliminates that component, reducing inventory lines and assembly time. Compared with a hex flange screw intended for thinner sheet, the DIN 6921 bolt is designed for through-bolting with a nut rather than thread-forming into a tapped hole.
Socket-head cap screws offer a recessed drive suited to flush or counter-bored installations but typically present a smaller bearing area under the head. The DIN 6921 flange bolt's external hex drive, by contrast, is accessible with open-ended spanners in confined spaces where a hex key or socket cannot be fully inserted, making it practical for field assembly.
Material & Grade
Material and grade information
- SS 304
- SS 316
Accurate Fastners supplies DIN 6921 flange bolts in SS 304, an austenitic grade containing approximately 18% chromium and 8% nickel. SS 304 offers good general corrosion resistance and is widely used in food-processing equipment, water-treatment systems, and light industrial frames. It is typically the starting point for most stainless steel fastener selections where aggressive chemical exposure is not a primary concern.
SS 316 adds molybdenum to the alloy, which generally improves resistance to chloride-bearing environments and certain process chemicals compared with SS 304. It is commonly selected for pharmaceutical machinery, coastal installations, and applications involving regular wash-down with cleaning agents. If your operating environment involves elevated chloride exposure or process fluids, the sales team at Accurate Fastners can help confirm which grade is more appropriate for your specific conditions.
Grades shown are those documented for this product in the Accurate Fastners brochure. General material notes are guidance only; confirm grade selection for your environment.
Technical Data
Technical specifications
| Product type | Bolt – DIN 6921 Flange Bolt |
|---|---|
| Material | Stainless steel |
| Material grade | SS 304, SS 316 |
| Applicable standard | DIN 6921 |
| Nominal diameter / size | M5 – M10 |
| Length | 10 mm – 100 mm |
| Thread type | Metric |
| Head / form | Hexagon head with integrated flange |
| Drive / tightening | External hex |
| Manufacturing process | Cold forged |
Sizes
Available sizes
Documented size range
M5 – M10
Documented length range
10 mm – 100 mm
Individual sizes within the documented range, thread pitches and lengths are confirmed at quotation stage.
Applications
Industrial applications
RO Water Purifier Frames
Stainless steel DIN 6921 flange bolts may be used to assemble the structural frames and panel brackets of RO water purifier units, where moisture exposure makes a corrosion-resistant fastener with broad bearing area a practical choice.
Solar Energy Mounting Structures
In solar panel racking systems, flange bolts can secure aluminium extrusion rails and module clamps. The integral flange distributes load across the rail profile, helping to avoid deformation of the aluminium substrate over time.
LED Lighting Enclosures
Thin-gauge steel or aluminium enclosures for LED luminaires benefit from the flange bolt's wider bearing footprint, which may reduce the risk of panel distortion when assembling housings on production lines without a separate washer.
Pharmaceutical Machinery Panels
SS 316 flange bolts are commonly considered for pharmaceutical machinery covers and access panels, where wash-down cleaning and hygiene requirements favour smooth, low-crevice fastener designs with good chemical resistance.
Food & Beverage Processing Equipment
In food-processing equipment frames and guards, stainless steel flange bolts offer a combination of corrosion resistance and simplified assembly, reducing the number of loose components that could be misplaced during maintenance routines.
Featured for: Solar Energy
Features & Selection
Features and selection considerations
Design features
Integral Flange
The flange is formed as one piece with the bolt head, eliminating a separate washer and reducing component count, potential misalignment, and assembly time in high-volume production environments.
Cold-Forged Construction
Cold forging refines the grain structure of the stainless steel, typically producing more consistent mechanical properties across the head-to-shank transition compared with fasteners produced by machining from bar.
External Hex Drive
The standard hexagonal drive is compatible with open-ended spanners, ring spanners, and sockets, supporting both manual and automated assembly with widely available tooling.
Metric Thread to DIN 6921
Metric threading manufactured to the DIN 6921 profile helps maintain dimensional interchangeability with mating nuts and threaded holes specified to the same standard.
Two Stainless Steel Grades
Availability in both SS 304 and SS 316 allows engineers to select the grade appropriate for their corrosion environment without switching supplier or fastener type.
Before you order
Diameter & Length
Confirm that the required diameter (M5–M10) and length (10–100 mm) are within the available range. Grip length—the unthreaded shank portion—should match the combined thickness of the clamped materials.
Grade Selection
Choose SS 304 for general indoor or low-moisture environments and SS 316 where chlorides, aggressive wash-down, or process chemicals are present. Confirm the choice with Accurate Fastners' sales team if the environment is uncertain.
Mating Components
Specify the mating nut grade and any washers for the bearing face on the nut side. Using a matching stainless grade for all joint components helps avoid galvanic incompatibility and simplifies maintenance records.
Quantity & Documentation
For bulk or project orders, provide quantity, diameter, length, and grade when requesting a quotation. Ask the sales team about material test certificates or compliance documentation relevant to your industry or client requirements.
FAQs
Frequently asked questions
What does DIN 6921 specify?
DIN 6921 is a German standard that defines the dimensional and geometric requirements for hexagon bolts with an integral flange. It covers head proportions, flange diameter, and thread profiles, helping to ensure consistent interchangeability across manufacturers producing to this standard.
Which stainless steel grades are available for these flange bolts?
Accurate Fastners supplies DIN 6921 flange bolts in SS 304 and SS 316. SS 304 suits general-purpose applications, while SS 316 is commonly selected where chloride exposure or chemical wash-down is a regular factor. Contact the sales team if you are uncertain which grade suits your environment.
What size range is available?
The available range is M5 to M10 in diameter and 10 mm to 100 mm in length. If your project requires dimensions outside this range, contact Accurate Fastners directly to discuss options and lead times.
Do I need a separate washer when using a DIN 6921 flange bolt?
A separate flat washer under the bolt head is generally not required because the integral flange already provides a wider bearing surface. However, a washer may still be advisable on the nut side depending on the substrate material and joint design requirements.
What other fasteners complement the DIN 6921 flange bolt in an assembly?
Matching stainless steel hex nuts and flat washers on the nut-bearing side are typical companions. Accurate Fastners also supplies a broad range of nuts, washers, and other bolts, so you can source compatible components from the same supplier and maintain consistent grade documentation.
How can I request a quotation for DIN 6921 flange bolts?
You can submit an enquiry through the online enquiry form on the Accurate Fastners website, send your requirements by email to export@accuratefastners.com, or contact the team via WhatsApp. Please include diameter, length, grade, and quantity for the quickest response.
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