M20 Form B Flat Washers (BS4320) - Stainless Steel (A2)


Key Features

  • M20 Metric Thread Size (20mm)
  • A2 Stainless Steel, also known as 18-8 or 304 Stainless Steel. Details.
  • For Use With Thread Size: M20 (20mm)
  • External Diameter (OD): 37mm
  • Thickness (T): 2.0mm
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M20 Form B Flat Washers (BS4320) - Stainless Steel (A2) Technical Specification

M20 Form B Flat Washers (BS4320) - Stainless Steel (A2) Drawing
External Diameter (D) Tolerance+0/-0.8mm
External Diameter (OD)37mm
For Use With Thread SizeM20 (20mm)
Internal Diameter (B) Tolerance+0.5/-0mm
Internal Diameter (ID)21mm
Manufacturing StandardBS4320
MaterialStainless Steel (A2)
Material SpecificationStainless Steel (A2)
Metric or Imperial?Metric
Thickness (T)2.0mm
Thickness (T) Tolerance+/-0.3mm

Product Certifications

Certificate of Conformity Included
Certificate of Conformity Included
RoHS Certified
RoHS Certified
REACH Certified
REACH Certified
Quality Approved

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M20 Form B Flat Washers (BS4320) - Stainless Steel (A2) Description

The M20 Form B Flat Washers (BS4320) - Stainless Steel (A2) has the following features:

  • BS4320 Manufacturing Standard
  • 21mm Internal Diameter (ID)
  • 37mm External Diameter (OD)
  • 2.0mm Thickness (T)
  • Stainless Steel (A2) Material
  • Stainless Steel (A2) Material Specification
  • Natural Finish
  • Metric Metric or Imperial?
  • +0.5/-0mm Internal Diameter (B) Tolerance
  • +0/-0.8mm External Diameter (D) Tolerance
  • +/-0.3mm Thickness (T) Tolerance
  • M20 (20mm) For Use With Thread Size

Discover more about the Metric Flat Washers range

Flat Washers, one of Accu's Washer & Spacer range, are designed primarily to enhance the load-bearing capabilities of a threaded fastener, and are compatible with a wide range of Precision Screws. Flat Washers are versatile components with a variety of uses, including spacing, pre-load indication, and wear-protection.

Flat Washers are available in several variants with varying diameters and thicknesses. The most commonly used washers are forms A, B and C, with more specialised variants such as Penny Washers also available. Flat washer variants range from those with small external diameters and thicknesses, to very large washers with large external diameters.

Where a flat surface is not required, components such as Countersunk Washers or Spring Washers may be preferable.


Accu's standard range of Flat Washers is manufactured from A2, A4 and Bumax Stainless Steel, with Chemical Matte Blackening available. All Stainless Steel Washers are resistant to tarnishing and corrosion, but A4 Stainless Steel is specifically designed for use in marine environments.

Flat Washers can also be manufactured from a variety of specialist materials, including Aluminium, Brass, Phosphor Bronze, Nylon, PEEK, Polycetal and Titanium. Fibre and Rubber Flat Washers are intended to be pliable for sealing purposes.

Metric Flat Washers

Metric Flat Washers are available in sizes ranging from M1 to M56. This category includes only metric flat washers – Imperial Flat Washers in imperial sizes are available separately.

Shipping Information

Shipping Destinations:Worldwide.
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Weight Band (100 items):Between 1kg and 5kg. Add to cart to calculate exact weights.

Component History

Product First Available:Sunday, June 28, 2015
Stock Last Updated:02:01 am
Tuesday, August 3, 2021
Specification Last Updated:Tuesday, August 3, 2021

APC / Barcodes

APC (Accu Product Code):HTW-M20-A2
EAN13 (International Article No.):5054328318144
ASIN (Amazon Stock Identification No.):ASIN not defined.