DIN127B: Quality Requirements and Applications

1. Quality Requirements (Key Specifications):

Spring washer DIN127B is the German standard specification for a specific type of flat spring washer (also commonly called a spring lock washer). Its key quality requirements and dimensional characteristics are strictly defined by the standard:

· Design: A single-coil, square-section helical spring washer. The ends are bent to form a continuous, offset helical shape.
· Function: The primary function is to provide a spring action (preload) and resist loosening via vibration by maintaining axial force in a bolted joint.
· Material: Typically made from spring steel (e.g., according to DIN 17223), stainless steel, or other non-ferrous metals depending on the application's corrosion and strength needs. The material must have the required elastic properties.
· Hardness & Elasticity: The washer must be hardened and tempered to achieve specified hardness levels (e.g., 42-50 HRC for common steel types). This ensures it exerts sufficient spring force without deforming permanently (taking a "set").
· Dimensions: The standard precisely defines dimensions for various nominal thread sizes (e.g., M4, M8, M20):
  · Outer diameter
  · Inner diameter (hole size)
  · Square section thickness and width
  · Free height
· Surface Finish: Often zinc-plated (blue-passivated or yellow), galvanized, or phosphate-coated for corrosion protection. Other coatings are possible.
· Performance: While not always explicitly tested in routine production, the design is intended to maintain load in the joint and prevent rotation of the nut or bolt head relative to the fastened parts.

2. Primary Applications and Usage:

DIN 127 B washers are used in a wide range of engineering and assembly applications where secure bolted connections are critical. Their main purposes are:

· Preventing Loosening from Vibration: A primary use is in assemblies subject to dynamic loads, shocks, or vibrations (e.g., automotive components, machinery, rail vehicles, electrical equipment). The spring tension helps keep the bolt tight.
· Maintaining Clamp Load: They compensate for slight settlement or thermal expansion/contraction in the joint by continuing to exert force.
· Compensating for Wear: They can take up wear in the joint over time.
· Providing a Defined Spring Element: Used where a specific, small amount of axial flexibility is needed in the assembly.
· Common Industries:
  · Automotive and vehicle manufacturing
  · General mechanical engineering and heavy machinery
  · Plant and equipment construction
  · Electrical enclosures and appliance manufacturing
  · Railway technology

Important Note on Modern Usage:
While DIN127B washers are still widely available and used, their effectiveness in preventing loosening under severe vibration has been questioned by modern studies. Standards like DIN 25201 and guidelines from organizations like the German Association of the Automotive Industry (VDA) now often recommend the use of superior locking elements (e.g., effective friction-locking nuts, adhesives, or serrated washers) for highly critical, vibration-prone applications. However, for general-purpose use and less severe conditions, DIN 127 B remains a common, cost-effective, and standardized solution.

In summary, DIN 127 B specifies a square-section helical spring lock washer designed to maintain preload and resist loosening in bolted joints, primarily for general engineering applications subject to vibration or dynamic loads.