Any specifications for MIL-SPEC hardware (such as AN, MS and NAS parts) includes the tests that parts are required to pass to qualify as MIL-SPEC parts.

As a service to its valued customers, WCL offers the following as a general guide to test and certification requirements for the MIL-SPEC hardware items it sells.

Flat Washers – MIL-SPEC designations for flat washers include, but are not limited to, AN960, MS15795, MS27183, NAS620, and NAS1252. These are covered by military procurement specification FF-W-92 which has, as minimum requirements.

  1. Chemical analysis                                                          
  2. Process certification on protective finish   
  3. Workmanship
  4. Magnetic permeability (stainless steel only)

Helical Spring Lockwashers – MIL-SPEC designations include, but are not limited to, MS35338, MS35340, MS51848, NAS1640 and NAS1676. These are covered by military procurement specification ASME B18.21.1 or FF-W-84 which has some, or all, of the following.

  1. Interlinking test
  2. Free height test
  3. Twist test
  4. Pressure test
  5. Hardness test
  6. Chemical analysis (mill certification acceptable)
  7. Magnetic permeability (on stainless steel)
  8. Process certification on protective finish
  9. Decarb test (on carbon steel)
  10. Embrittlement test (electro plated)

Spring Washers – Curved, Wave And Belleville – MIL-SPEC designations for spring washers include but are not limited to, M12133/1 and M12133/2 and are covered by mil­itary specification MIL-W-12133 which has, as minimum requirements:

  1. Chemical analysis
  2. Process certification on protective coating and surface treatment
  3. Inspection for cracks
  4. Hardness test
  5. Decarburization (carbon steel only)
  6. Load Deflection
  7. Permanent set
  8. Repeated loading

Tooth Lockwashers – MIL-SPEC designations for tooth lockwashers include, but are not limited to MS35333, MS35335, MS35336, MS35790 and MS45904. These are covered by military procurement specification ASME B18.21.1 or FF-W-100 which has some or all of the following.

  1. Hardness test
  2. Process certification on protective finish
  3. Chemical analysis
  4. Compression and flattening test
  5. Spread test
  6. Twist test
  7. Temper test
  8. Decarb test (on carbon steel)
  9. Embrittlement test (electro plated)

The above list provides a guide relating to the most popular types of MIL-SPEC washers. It should not be construed as a complete list of all military specifications and documents pertaining to washers or as a list of all tests or analysis that may be required.

Many OEM’s also have special requirements (including testing) that must be met to be in compliance with their part spec­ifications and purchase requirements.

Review all relevant documents carefully before requesting quotations to avoid unexpected costs for testing and analysis. When in doubt, discuss the requirements with your WCL sales associates.

Remember, if it has not been properly tested, it is not MIL-SPEC hardware.