ASME · ANSI / ASME B18.21.2M

ANSI / ASME B 18.21.2M Standard: Metric Lock Washers and Spring Retainers

Technical Specification and Scope of Application

The ASME B 18.21.2M standard regulates geometric parameters, physical-mechanical characteristics, and inspection test protocols for metric spring and tooth lock washers. This regulatory documentation is fundamental for design engineers when developing assemblies with high requirements for vibration resistance and threaded connection reliability.

EV Group China notes that the information in this standard is not exhaustive for all nomenclature items. To clarify the availability of specific sizes and the possibility of supplying non-standard products, we recommend sending inquiries to our technical specialists.

Note: The terminology used to identify products in this standard is descriptive in nature and does not guarantee absolute locking effectiveness in all types of dynamic loads.

Compliance with International Standards

Currently, there is no direct equivalent to this standard in the ISO system, which makes ASME B 18.21.2M a unique industry document for metric fasteners.

Classification of Lock Washers

Spring Locking Elements:

The standard establishes requirements for two main versions of spring washers: standard and heavy-duty.

Toothed and Specialized Retainers:

The technical regulation covers the following element modifications:

  • Washers with an external toothed profile;
  • Flat-type lock washers with two locking tabs;
  • Washers with an external protrusion;
  • Washers with internal tooth engagement and other specialized configurations.

Dimensional Accuracy

All linear parameters provided in the standard's tables are expressed in millimeters (mm) and correspond to the state of the products before the application of protective anti-corrosion coatings or heat treatment, unless otherwise specified in the order.

Terminology Base

For the correct interpretation of definitions and technical characteristics of locking elements, one should refer to the ASME B 18.12 standard, "Glossary of Terms for Mechanical Fasteners".