DIN 6923 Guide for Selecting Hexagonal Flange Nuts

What Is a DIN 6923 Hex Flange Nut?

DIN 6923 is the German Institute for Standardization (Deutsches Institut für Normung) standard for hex flange nuts, corresponding to GB 6177 in the Chinese national standard system. The standard specifies dimensions, tolerances, and technical requirements for hex nuts with an integrated flange face, covering nominal diameters from M5 to M20.

The core design concept of a flange nut is the one-piece integration of the flange and nut body. The flange acts as a non-rotating washer, distributing clamp load evenly across the mating surface. This lowers surface pressure and prevents soft materials from being damaged or deformed during tightening. The serrated teeth on the bottom of the flange further enhance anti-loosening performance—the teeth bite into the mating surface when tightened, creating a mechanical locking effect that resists vibration-induced loosening.

The standard covers both coarse and fine thread forms, with materials including carbon steel and stainless steel, and is widely used in automotive, machinery, construction, and electronics applications.

Key Technical Features

Integrated Flange Design, No Washer Needed

The most notable advantage of DIN 6923 flange nuts is their built-in washer function. The flange face increases the bearing area, distributing clamp load more evenly and preventing thin sheet metal or soft materials from denting or deforming during bolt tightening. This design eliminates the need for a separate flat washer, simplifying assembly while reducing part count and inventory management costs. The flange also helps bridge oversized holes or slots, improving assembly flexibility.

Serrated Anti-Slip Mechanism

Serrated flange nuts feature single-direction spiral teeth on the bottom of the flange, with the tooth pattern running opposite to the tightening direction. Once the nut is tightened into place, the teeth embed into the workpiece surface, creating continuous friction that effectively prevents loosening from vibration or external forces. When removed, the teeth leave impressions rather than deep gouges in the workpiece, balancing anti-loosening performance with surface protection.

Materials and Property Grades

DIN 6923 flange nuts are available in carbon steel and stainless steel. Carbon steel property grades include 4, 5, 6, 8, 10, and 12, with Grades 8 and 10 being the most common. Stainless steel grades include A2-50, A2-70, and A4-70 for applications requiring corrosion resistance. Surface finishes include zinc plating (yellow, white, and blue zinc), black oxide, and hot-dip galvanizing.

Metric M4-M20 Size Range

The DIN 6923 standard itself specifies nominal diameters from M5 to M20. While M3 and M4 sizes are common on the market, they do not strictly fall under the DIN 6923 standard—many manufacturers produce these smaller sizes based on the standard's dimensional system to meet market demand. For thread pitch, fine thread options are generally available for M8 and above, such as M10 fine thread at 1.25 mm pitch and M12 fine thread at 1.5 mm pitch.

Detailed Application Areas

Automotive Industry

Automotive manufacturing is one of the core application areas for DIN 6923 flange nuts. These standard nuts are widely used for fastening body, chassis, and other components. Specific applications include:

• Body structure: The flange distributes load and prevents thin sheet metal from deforming during tightening, making it suitable for securing body panels and brackets

• Chassis systems: The anti-loosening performance of serrated flanges keeps suspension and steering components tight through continuous vibration

• Engine accessories: Securing various accessories and line connections in vibrating environments

Industrial Machinery

In industrial machinery, these standard nuts are suited to component assembly and fastening across a wide range of equipment, including:

• Machine tools and construction machinery: Keeping structures stable under operating vibration

• Agricultural machinery: Serrated flange nuts are widely used as a reliable locking solution in transport equipment and farm machinery

• Pump, valve, and piping systems: Flange nuts are commonly used in pipe connections to provide even sealing pressure

Construction

Construction demands long-term stability from fasteners. DIN 6923 flange nuts are used in:

• Steel structure connection nodes

• Pipe installation and securing

• Fastening of metal components

The larger contact area of the flange face helps distribute loads evenly in steel connections, while the serrated anti-slip feature adds long-term reliability.

Electronics and Precision Equipment

In electronics and automation equipment, these nuts are used for precision fastening. Small M4 and M5 sizes fit installation needs in tight spaces, and the flange design prevents damage to precision surfaces.

Furniture and Hardware Assembly

Furniture manufacturing, shelving assembly, and kitchen and bath fixture installation also use DIN 6923 flange nuts. The integrated design simplifies assembly, and the serrated anti-slip feature keeps connections from loosening over long-term use.

Selection Guide

Consider the following factors when choosing DIN 6923 flange nuts:

Summary

The DIN 6923 standard provides a complete technical specification for metric hex flange nuts, covering M5-M20 sizes, coarse and fine threads, and carbon and stainless steel materials. The integrated flange design combines washer function with the nut body, eliminating the need for a separate washer while distributing load to protect the workpiece surface. Serrated flange types bite into the mating surface through single-direction teeth, providing reliable anti-loosening performance in vibrating environments. These standard nuts are widely used in automotive manufacturing, industrial machinery, construction, electronics, and furniture assembly, making them an important choice in the metric fastener system for both convenience and reliability.