Metric Flat Washer BS 4320 Size Comparison

Metric flat washers to the British Standard BS4320 range from forms A to G and are popular in that they give size options that the German Din flat washer standard does not. BS4320 Form A flat washers are virtually identical to Din125A flat washers.

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Flat washers are a thin circular plate with a hole in the middle.

Flat washers are typically used to distribute the load of a threaded fastener, Bolt  Screw or Nut.

Flat washers are also used as a surface protection pad or spacer.

Flat washer "type" is not to be confused with "form".

Metric series washers to British standard 4320 Metal Washers (BS4320), written in 1968, used the term "form".

Flat washer forms go from A to G and dictate the outside diameter and thickness of flat washers.

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BS4320 Form A:  Normal diameter   Normal thickness

BS4320 Form B:  Normal diameter   Light thickness

BS4320 Form C:  Large diameter     Normal thickness

BS4320 Form D:  Large diameter     Light thickness

BS4320 Form E:  Larger diameter    Normal thickness

BS4320 Form F:  Larger diameter    Normal thickness

BS4320 Form G: Largest diameter  Larger thickness

BS4320 flat washer