BS 916 Hexagon Head Screw

Hexagon head Screws

BS 916 Hexagon Head Screw

Nominal size
D		 No. of
threads
per inch		 Width across flats
A
hex. and square		 Approx. max.
width across
corners
C		 Radius
under
head
R		 Thickness of head
F
hex.and sqaure		 Nominal size
D
B.S.W max. min. hex. square. max. max. basic.
in. in. in. in. in. in. in. in. in.
¼ 20 0.445 0.435 0.51 0.63 ¹⁄₃₂ 0.186 0.166 ¼
⁵⁄₁₆ 18 0.525 0.515 0.61 0.74 ¹⁄₃₂ 0.228 0.208 ⁵⁄₁₆
⅜ 16 0.600 0.585 0.69 0.85 ¹⁄₃₂ 0.270 0.250 ⅜
⁷⁄₁₆ 16 0.600 0.585 0.69 0.85 ¹⁄₃₂ 0.270 0.250 ⁷⁄₁₆
½ 12 0.820 0.800 0.95 1.16 ¹⁄₃₂ 0.363 0.333 ½
⁹⁄₁₆ 12 0.920 0.900 1.06 1.30 ³⁄₆₄ 0.405 0.375 ⁹⁄₁₆
⅝ 0.11 1.010 0.985 1.17 1.43 ³⁄₆₄ 0.447 0.417 ⅝
¾ 10 1.200 1.175 1.39 1.70 ³⁄₆₄ 0.530 0.500 ¾
⅞ 9 1.300 1.270 1.50 1.84 ¹⁄₁₆ 0.623 0.583 ⅞
1 8 1.480 1.450 1.71 2.09 ¹⁄₁₆ 0.706 0.666 1
1⅛ 7 1.670 1.640 1.93 2.36 ⅛ 0.79 0.75 1⅛
1¼ 7 1.860 1.815 215 2.63 ⅛ 0.89 0.83 1¼
1⅜a 6 2.050 2.005 2.37 2.90 ⅛ 0.98 0.92 1⅜a
1½ 6 2.220 2.175 2.56 3.14 ⅛ 1.06 1.00 1½
1⅝a 5 2.410 2.365 2.78 3.41 ⅛ 1.18 1.08 1⅝a
1¾ 5 2.580 2.520 2.98 3.65 ⅛ 1.27 1.17 1¾
2 4.5 2.760 2.700 3.19 3.90 ⅛ 1.43 1.33 2
2¼ 4 3.150 3.090 3.64 3.90 ⅛ 1.43 1.33 2¼
2½ 4 3.550 3.490 4.10 5.02 ³⁄₁₆ 1.77 1.67 2½
2¾ 3.5 3.890 3.830 4.49 5.50 ³⁄₁₆ 1.93 1.83 2¾
3 3.5 4.180 4.080 4.83 5.91 ³⁄₁₆ 2.15 2.00 3
3¼a 3.25 4.530 4.430 5.23 6.41 ¼ 2.32 2.17 3¼a
3½ 3.25 4.850 4.750 5.60 6.86 ¼ 2.48 2.33 3½
3¾a 3. 5.180 5.080 5.98 7.33 ¼ 2.65 2.50 3¾a
4 3 5.550 5.450 6.41 7.85 ¼ 2.82 2.67 4
4½ 2.875 6.380 6.255 7.37 9.02 ¼ 3.20 3.00 4½
5 2.750 7.300 7.175 8.43 10.32 ¼ 3.53 3.33 5
5½ 2.625 8.350 8.225 9.64 11.81 ¼ 3.87 3.67 5½
5½ 2.5 9.450 9.325 10.91 13.36 ¼ 4.20 4.00 6
a To be dispensed with wherever possible.