BS 4320 British Standard For Metal Washers

BS 4320 British Standard For Metal Washers

BS 4320 British Standard For Metal Washers (Normal Diameter Sizes)

Nominal Size of Bolt or Screw Inside Diameter Outside Diameter Thickness
Form A Normal Range Form B Light Range
Nom Max Min Nom Max Min Nom Max Min Nom Max Min
BS 4320 - M1.0 1.1 1.25 1.1 2.5 2.5 2.3 0.3 0.4 0.2 ... ... ...
BS 4320 - M1.2 1.3 1.45 1.3 3 3 2.8 0.3 0.4 0.2 ... ... ...
BS 4320 - M1.4 1.5 1.65 1.5 3 3 2.8 0.3 0.4 0.2 ... ... ...
BS 4320 - M1.6 1.7 1.85 1.7 4 4 3.7 0.3 0.4 0.2 ... ... ...
BS 4320 - M2.0 2.2 2.35 2.2 5 5 4.7 0.3 0.4 0.2 ... ... ...
BS 4320 - M2.2 2.4 2.55 2.4 5 5 4.7 0.5 0.6 0.4 ... ... ...
BS 4320 - M2.5 2.7 2.85 2.7 6.5 6.5 6.2 0.5 0.6 0.4 ... ... ...
BS 4320 - M3 3.2 3.4 3.2 7 7 6.7 0.5 0.6 0.4 ... ... ...
BS 4320 - M3.5 3.7 3.9 3.7 7 7 6.7 0.5 0.6 0.4 ... ... ...
BS 4320 - M4 4.3 4.5 4.3 9 9 8.7 0.8 0.9 0.7 ... ... ...
BS 4320 - M4.5 4.8 5 4.8 9 9 8.7 0.8 0.9 0.7 ... ... ...
BS 4320 - M5 5.3 5.5 5.3 10 10 9.7 1 1.1 0.9 ... ... ...
BS 4320 - M6 6.4 6.7 6.4 12.5 12.5 12.1 1.6 1.8 1.4 0.8 0.9 0.7
BS 4320 - M7 7.4 7.7 7.4 14 14 13.6 1.6 1.8 1.4 0.8 0.9 0.7
BS 4320 - M8 8.4 8.7 8.4 17 17 16.6 1.6 1.8 1.4 1 1.1 0.9
BS 4320 - M10 10.5 10.9 10.5 21 21 20.5 2 2.2 1.8 1.25 1.45 1.05
BS 4320 - M12 13 13.4 13 24 24 23.5 2.5 2.7 2.3 1.6 1.8 1.4
BS 4320 - M14 15 15.4 15 28 28 27.5 2.5 2.7 2.3 1.6 1.8 1.4
BS 4320 - M16 17 17.4 17 30 30 29.5 3 3.3 2.7 2 2.2 1.8
BS 4320 - M18 19 19.5 19 34 34 33.2 3 3.3 2.7 2 2.2 1.8
BS 4320 - M20 21 21.5 21 37 37 36.2 3 3.3 2.7 2 2.2 1.8
BS 4320 - M22 23 23.5 23 39 39 38.2 3 3.3 2.7 2 2.2 1.8
BS 4320 - M24 25 25.5 25 44 44 43.2 4 4.3 3.7 2.5 2.7 2.3
BS 4320 - M27 28 28.5 28 50 50 49.2 4 4.3 3.7 2.5 2.7 2.3
BS 4320 - M30 31 31.6 31 56 56 55 4 4.3 3.7 2.5 2.7 2.3
BS 4320 - M33 34 34.6 34 60 60 59 5 5.6 4.4 3 3.3 2.7
BS 4320 - M36 37 37.6 37 66 66 65 5 5.6 4.4 3 3.3 2.7
BS 4320 - M39 40 40.6 40 72 72 71 6 6.6 5.4 3 3.3 2.7

BS 4320 British Standard For Metal Washers (Large Diameter Sizes)

Nominal Size of Bolt or Screw Inside Diameter Outside Diameter Thickness
Form C Normal Range Form D Light Range
Nom Max Min Nom Max Min Nom Max Min Nom Max Min
BS 4320 - M4 4.3 4.5 4.3 10 10 9.7 0.8 0.9 0.7 ... ... ...
BS 4320 - M5 5.3 5.5 5.3 12.5 12.5 12.1 1 1.1 0.9 ... ... ...
BS 4320 - M6 6.4 6.7 6.4 14 14 13.6 1.6 1.8 1.4 0.8 0.9 0.7
BS 4320 - M8 8.4 8.7 8.4 21 21 20.5 1.6 1.8 1.4 1 1.1 0.9
BS 4320 - M10 10.5 10.9 10.5 24 24 23.5 2 2.2 1.8 1.25 1.45 1.05
BS 4320 - M12 13 13.4 13 28 28 27.5 2.5 2.7 2.3 1.6 1.8 1.4
BS 4320 - M14 15 15.4 15 30 30 29.5 2.5 2.7 2.3 1.6 1.8 1.4
BS 4320 - M16 17 17.4 17 34 34 33.2 3 3.3 2.7 2 2.2 1.8
BS 4320 - M18 19 19.5 19 37 37 36.2 3 3.3 2.7 2 2.2 1.8
BS 4320 - M20 21 21.5 21 39 39 38.2 3 3.3 2.7 2 2.2 1.8
BS 4320 - M22 23 23.5 23 44 44 43.2 3 3.3 2.7 2 2.2 1.8
BS 4320 - M24 25 25.5 25 50 50 49.2 4 4.3 3.7 2.5 2.7 2.3
BS 4320 - M27 28 28.5 28 56 56 55 4 4.3 3.7 2.5 2.7 2.3
BS 4320 - M30 31 31.6 31 60 60 59 4 4.3 3.7 2.5 2.7 2.3
BS 4320 - M33 34 34.6 34 66 66 65 5 5.6 4.4 3 3.3 2.7
BS 4320 - M36 37 37.6 37 72 72 71 5 5.6 4.4 3 3.3 2.7
BS 4320 - M39 40 40.6 40 77 77 76 6 6.6 5.4 3 3.3 2.7
  • All dimensions are in millimeters.
  • Nominal bolt or screw sizes shown in parentheses are nonpreferred.