Machinery's Handbook, 31st Edition
2088
WHITWORTH THREADS Table 3. British Standard Whitworth (BSW) and British Standard Fine (BSF) Screw Thread Series—Basic Dimensions BS 84:1956 (obsolescent) Nominal Size, Inches Threads per Inch Pitch, Inches Depth of Thread, Inches Major Diameter, Inches Effective Diameter, Inches Minor Diameter, Inches Area at Bottom ofThread, Sq. in. Tap Drill Dia.
Coarse Thread Series (BSW)
40 24 20 18 16 14 12 12 11 11 10
0.02500 0.0160 0.1250 0.1090 0.9030 0.04167 0.0267 0.1875 0.1608 0.1341 0.05000 0.0320 0.2500 0.2180 0.1860 0.05556 0.0356 0.3125 0.2769 0.2413 0.06250 0.0400 0.3750 0.3350 0.2950 0.07143 0.0457 0.4375 0.3918 0.3461 0.08333 0.0534 0.5000 0.4466 0.3932 0.08333 0.0534 0.5625 0.5091 0.4557 0.09091 0.0582 0.6250 0.5668 0.5086 0.09091 0.0582 0.6875 0.6293 0.5711 0.10000 0.0640 0.7500 0.6860 0.6220 0.11111 0.0711 0.8750 0.8039 0.7328 0.12500 0.0800 1.0000 0.9200 0.8400 0.14286 0.0915 1.1250 1.0335 0.9420 0.14286 0.0915 1.2500 1.1585 1.0670 0.16667 0.1067 1.5000 1.3933 1.2866 0.20000 0.1281 1.7500 1.6219 1.4938 0.22222 0.1423 2.0000 1.8577 1.7154 0.25000 0.1601 2.2500 2.0899 1.9298 0.25000 0.1601 2.5000 2.3399 2.1798 0.28571 0.1830 2.7500 2.5670 2.3840 0.28571 0.1830 3.0000 2.8170 2.6340 0.30769 0.1970 3.2500 3.0530 2.8560 0.30769 0.1970 3.5000 3.3030 3.1060 0.33333 0.2134 3.7500 3.5366 3.3232 0.33333 0.2134 4.0000 3.7866 3.5732 0.36364 0.2328 5.0000 4.7672 4.5344 0.40000 0.2561 6.0000 5.7439 5.4878 0.03125 0.0200 0.1875 0.1675 0.1475 0.03571 0.0229 0.2188 0.1959 0.1730 Fine Thread Series (BSF) 0.03846 0.0246 0.2500 0.2254 0.2008 0.03846 0.0246 0.2812 0.2566 0.2320 0.04545 0.0291 0.3125 0.2834 0.2543 0.05000 0.0320 0.3750 0.3430 0.3110 0.05556 0.0 356 0.4375 0.4019 0.3363 0.06250 0.0400 0.5000 0.4600 0.4200 0.06250 0.0400 0.5625 0.5225 0.4825 0.07143 0.0457 0.6250 0.5793 0.5336 0.07143 0.0457 0.6875 0.6418 0.5961 0.08333 0.0534 0.7500 0.6966 0.6432 0.09091 0.0582 0.8750 0.8168 0.7586 0.10000 0.0640 1.0000 0.9360 0.8720 0.11111 0.0711 1.1250 1.0539 0.9828 0.11111 0.0711 1.2500 1.1789 1.1078 0.12500 0.0800 1.3750 1.2950 1.2150 0.12500 0.0800 1.5000 1.4200 1.3400 0.12500 0.0800 1.6250 1.5450 1.4650 0.14286 0.0915 1.7500 1.6585 1.5670 0.14286 0.0915 2.0000 1.9085 1.8170 0.16667 0.1067 2.2500 2.1433 2.0366 0.16667 0.1067 2.5000 2.3933 2.2866 0.16667 0.1067 2.7500 2.6433 2.5366 0.20000 0.1281 3.0000 2.8719 2.7438 0.20000 0.1281 3.2500 3.1219 2.9938 0.22222 0.1423 3.5000 3.3577 3.2154 0.22222 0.1423 3.7500 3.6077 3.4654 0.22222 0.1423 4.0000 3.8577 3.7154 0.25000 0.1601 4.2500 4.0899 3.9298
0.0068 0.0141 0.0272 0.0457 0.0683 0.0941 0.1214 0.1631 0.2032 0.2562 0.3039 0.4218 0.5542 0.6969 0.8942 1.3000 1.7530 2.3110 2.9250 3.7320 4.4640 5.4490 6.4060 7.5770 8.6740 10.0300 12.9100 16.1500 19.7300 23.6500 0.0171 0.0235 0.0317 0.0423 0.0508 0.0760 0.1054 0.1385 0.1828 0.2236 0.2791 0.3249 0.4520 0.5972 0.7586 0.9639 1.1590 1.4100 1.6860 1.9280 2.5930 3.2580 4.1060 5.0540 5.9130 7.0390 8.1200 9.4320 10.8400 12.1300
2.55 mm 3.70 mm 5.10 mm 6.50 mm 7.90 mm 9.30 mm 10.50 mm 12.10. mm 13.50 mm 15.00 mm 16.25 mm 19.25 mm 22.00 mm 24.75 mm 28.00 mm 33.50 mm 39.00 mm 44.50 mm
a
1 ∕ 8
3 ∕ 16 1 ∕ 4 5 ∕ 16 3 ∕ 8 7 ∕ 16 1 ∕ 2 9 ∕ 16 5 ∕ 8
a
a
11 ∕ 16
3 ∕ 4 7 ∕ 8
9 8 7 7 6 5 4 4
1
1 1 ∕ 8 1 1 ∕ 4 1 1 ∕ 2 1 3 ∕ 4 2 1 ∕ 4 2 1 ∕ 2 2 3 ∕ 4 2 3 1 ∕ 4 3 1 ∕ 2 3 3 ∕ 4 4 1 ∕ 2 5 1 ∕ 2 3 4 5 6
4.5
Tap drill diameters shown in
3.5 3.5
3.25 3.25
a
this column are recommended sizes listed in BS 1157:1975 and provide from 77 to 87% of full thread.
3 3
a
2.875 0.34783 0.2227 4.5000 4.2773 4.0546 2.625 0.38095 0.2439 5.5000 5.2561 5.0122 2.75
2.5
32 28 26 26 22 20 18 16 16 14 14 12 11 10
4.00 mm 4.60 mm 5.30 mm 6.10 mm 6.80 mm 8.30 mm 9.70 mm 11.10 mm 12.70 mm 14.00 mm 15.50 mm 16.75 mm 19.75 mm 22.75 mm 25.50 mm 28.50 mm 31.50 mm 34.50 mm
a , b
3 ∕ 16 7 ∕ 32 1 ∕ 4 9 ∕ 32 5 ∕ 16 3 ∕ 8 7 ∕ 16 1 ∕ 2
a
a
9 ∕ 16 5 ∕ 8 11 ∕ 16
a
3 ∕ 4 7 ∕ 8
1
9 9 8 8 8 7 7 6 6 6 5 5
1 1 ∕ 8 1 1 ∕ 4 1 3 ∕ 8 1 1 ∕ 2 1 5 ∕ 8 1 3 ∕ 4 2 1 ∕ 4 2 2 1 ∕ 2 2 3 ∕ 4 3 1 ∕ 4 3 3 1 ∕ 2 3 3 ∕ 4 4 1 ∕ 4 4
a
a
Tap drill sizes listed in this column are recommended sizes shown in BS 1157:1975 and provide from 78 to 88% of full thread.
4.5 4.5 4.5
4
a To be dispensed with wherever possible. b The use of number 2 BA threads is recommended in place of 3/16-inch BSF thread, see page 2114.
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