BS 4190 Standard

Dimensions of ISO metric black hexagon head bolts and screws

Hexagon head bolt

Hexagon head screw

1 2 3 4 5 6 7 8 9 10 11 12 13
Nominal size and thread diameter
d		 Pitch of thread
(coarse pitch series)		 Diameter of unthreaded shank
d		 Width across flats
s		 Width across corners
e		 Height of head
k		 Radius under head
r		 Washer face dia.
(see note 2)
dw		 Depth of washer face
c
max. min. max. min. max. min. max. min. max. min. max.
M5 0.8 5.48 4.52 8.00 7.64 9.2 8.63 3.875 3.125 0.35 6.8 0.5
M6 1 6.48 5.52 10.00 9.64 11.5 10.89 4.375 3.625 0.40 8.7 0.5
M8 1.25 8.58 7.42 13.00 12.57 15.0 14.20 5.875 5.125 0.8 11.5 0.6
M10 1.5 10.58 9.42 17.00 16.57 19.6 18.72 7.45 6.55 0.8 15.5 0.6
M12 1.75 12.70 11.30 19.00 18.48 21.9 20.88 8.45 7.55 1.25 17.2 0.6
M16 2 16.70 15.30 24.00 23.16 27.7 26.17 10.45 9.55 1.25 22.0 0.8
M20 2.5 20.84 19.16 30.00 29.16 34.6 32.95 13.90 12.10 1.78 27.7 0.8
M22 2.5 22.84 21.16 32.00 31.00 36.9 35.03 14.90 13.10 1.78 --- ---
M24 3 24.84 23.16 36.00 35.00 41.6 39.55 15.90 14.10 1.78 33.2 0.8
M27 3 27.84 26.16 41.00 40.00 47.3 45.20 17.90 16.10 2.28 --- ---
M30 3.5 30.84 29.16 46.00 45.00 53.1 50.85 20.05 17.95 2.28 42.7 0.8
M33 3.5 34.00 32.00 50.00 49.00 57.7 55.37 22.05 19.95 2.28 --- ---
M36 4 37.00 35.00 55.00 53.80 63.5 60.79 24.05 21.95 2.7 51.1 0.8
M39 4 40.00 38.00 60.00 58.80 69.3 66.44 26.05 23.95 2.7 --- ---
M42 4.5 43.00 41.00 65.00 63.80 75.1 72.09 27.05 24.95 2.8 60.8 1.0
M45 4.5 46.00 44.00 70.00 68.80 80.8 77.74 29.05 26.95 3.3 --- ---
M48 5 49.00 47.00 75.00 73.80 86.6 83.39 31.05 28.95 3.8 70.8 1.0
M52 5 53.20 50.80 80.00 78.80 92.4 89.04 34.25 31.75 4.7 --- ---
M56 5.5 57.20 54.80 85.00 83.60 98.1 94.47 36.25 33.75 4.9 --- ---
M60 5.5 61.20 58.80 90.00 88.60 103.9 100.12 39.25 36.75 4.9 --- ---
M64 6 65.20 62.80 95.00 93.60 109.7 105.77 41.25 38.75 4.9 --- ---
M68 6 69.20 62.80 100.00 98.60 115.5 111.42 44.25 41.75 4.9 --- ---

NOTE 1: Sizes in brackets are non-preferred.
NOTE 2: Calculations of washer face diameters for other sizes may be obtained from the following formulae:
    1) for sizes up to and including M20:
        washer face diameter (min.) = smin. – IT16;
    2) for sizes over M20:
        washer face diameter (min.) = smin. – IT17;
where
    IT stands for standard tolerance, and belongs to the ISO series of tolerances (see BS EN 20286-1 and BS EN 20286-2).