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BS 4320

FLAT WASHER


BS 4320

Steel Hardness: 100HV
Finish: Self, Black, Bright Zinc, Hot Dip Galvanized

Dimensions
Nominal Washer Size Inside Diameter (ID) Outside Diameter (OD) Thickness (s)
Min. Max. Min. Max. FORM A FORM B
Nom. Max. Min. Nom. Max. Min.
M3 3.2 3.4 6.7 7 0.5 0.6 0.4 - - -
M4 4.3 4.5 8.7 9 0.8 0.9 0.7 - - -
M5 5.3 5.5 9.7 10 1 1.1 0.9 - - -
M6 6.4 6.7 12.1 12.5 1.6 1.8 1.4 0.8 0.9 0.7
M8 8.4 8.7 16.6 17 1.6 1.8 1.4 1 1.1 0.9
M10 10.5 10.9 20.5 21 2 2.2 1.8 1.25 1.45 1.05
M12 13 13.4 23.5 24 2.5 2.7 2.3 1.6 1.8 1.4
(M14) 15 15.4 27.5 28 2.5 2.7 2.3 1.6 1.8 1.4
M16 17 17.4 29.5 30 3 3.3 2.7 2 2.2 1.8
(M18) 19 19.5 33.2 34 3 3.3 2.7 2 2.2 1.8
M20 21 21.5 36.2 37 3 3.3 2.7 2 2.2 1.8
(M22) 23 23.5 38.2 39 3 3.3 2.7 2 2.2 1.8
M24 25 25.5 43.2 44 4 4.3 3.7 2.5 2.7 2.3
(M27) 28 28.5 49.2 50 4 4.3 3.7 2.5 2.7 2.3
M30 31 31.6 55 56 4 4.3 3.7 2.5 2.7 2.3
(M33) 34 34.6 59 60 5 5.6 4.4 3 3.3 2.7
M36 37 37.6 65 66 5 5.6 4.4 3 3.3 2.7
(M39) 40 40.6 71 72 6 6.6 5.4 3 3.3 2.7
Nominal Washer Size Inside Diameter (ID) Outside Diameter (OD) Thickness (s)
Min. Max. Min. Max. FORM C FORM D
Nom. Max. Min. Nom. Max. Min.
M4 4.3 4.5 9.7 10 0.8 0.9 0.7 - - -
M5 5.3 5.5 12.1 12.5 1 1.1 0.9 - - -
M6 6.4 6.7 13.6 14 1.6 1.8 1.4 0.8 0.9 0.7
M8 8.4 8.7 20.5 21 1.6 1.8 1.4 1 1.1 0.9
M10 10.5 10.9 23.5 24 2 2.2 1.8 1.25 1.45 1.05
M12 13 13.4 27.5 28 2.5 2.7 2.3 1.6 1.8 1.4
(M14) 15 15.4 29.5 30 2.5 2.7 2.3 1.6 1.8 1.4
M16 17 17.4 33.2 34 3 3.3 2.7 2 2.2 1.8
(M18) 19 19.5 36.2 37 3 3.3 2.7 2 2.2 1.8
M20 21 21.5 38.2 39 3 3.3 2.7 2 2.2 1.8
(M22) 23 23.5 43.2 44 3 3.3 2.7 2 2.2 1.8
M24 25 25.5 49.2 50 4 4.3 3.7 2.5 2.7 2.3
(M27) 28 28.5 55 56 4 4.3 3.7 2.5 2.7 2.3
M30 31 31.6 59 60 4 4.3 3.7 2.5 2.7 2.3
(M33) 31 31.6 65 66 5 5.6 4.4 3 3.3 2.7
M36 37 37.6 71 72 5 5.6 4.4 3 3.3 2.7
(M39) 40 40.6 76 77 6 6.6 5.4 3 3.3 2.7
Nominal Washer Size Inside Diameter (ID) Outside Diameter (OD) Thickness (s)
Min. Max. Min. Max. FORM F
Nom. Max. Min.
M8 9 9.4 20.2 21 1.6 1.9 1.3
M10 11 11.5 23.2 24 2 2.3 1.7
M12 14 14.5 27.2 28 2.5 2.8 2.2
(M14) 16 16.5 29.2 30 2.5 2.8 2.2
M16 18 18.5 32.8 34 3 3.6 2.4
(M18) 20 20.6 35.8 37 3 3.6 2.4
M20 22 22.6 37.8 39 3 3.6 2.4
(M22) 24 24.6 42.8 44 3 3.6 2.4
M24 26 26.6 48.8 50 4 4.6 3.4
(M27) 30 30.6 54.5 56 4 4.6 3.4
M30 33 33.8 58.5 60 4 4.6 3.4
(M33) 36 36.8 64.5 66 5 6 4
M36 39 39.8 70.5 72 5 6 4
(M39) 42 42.8 75.5 77 6 7 5