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BS 93 British Association (B.A.) Screw Threads
INDEX of THREAD DATA CHARTS

BS 93 British Association (BA) Screw Threads Data Charts

BS93:2008


British Association Standard Screw Threads are used mainly for instruments and clocks.
The BA-series screw threads should not be used for new designs. Instead use the M-series screw threads.

BS 93: British Association (BA) Screw Threads
Limits and Tolerances for BA Internal Screw Threads given in mm
Nominal
Size
Pitch
P

Major Diameter

Effective/Pitch
Diameter

Minor Diameter
D Min D2 Min Max D1 Min Max
#16 BA 0.19 0.790 0.675 0.730 0.560 0.630
#15 BA 0.21 0.900 0.775 0.830 0.650 0.730
#14 BA 0.23 1.000 0.860 0.920 0.720 0.805
#13 BA 0.25 1.200 1.050 1.110 0.900 0.995
#12 BA 0.28 1.300 1.130 1.195 0.960 1.065
#11 BA 0.31 1.500 1.315 1.380 1.130 1.245
#10 BA 0.35 1.700 1.490 1.560 1.280 1.410
#9 BA 0.39 1.900 1.665 1.740 1.430 1.575
#8 BA 0.43 2.200 1.940 2.020 1.680 1.840
#7 BA 0.48 2.500 2.210 2.300 1.920 2.100
#6 BA 0.53 2.800 2.480 2.575 2.160 2.360
#5 BA 0.59 3.200 2.845 2.945 2.490 2.710
#4 BA 0.66 3.600 3.205 3.315 2.810 3.060
#3 BA 0.73 4.100 3.660 3.780 3.220 3.495
#2 BA 0.81 4.700 4.215 4.340 3.730 4.035
#1 BA 0.90 5.300 4.760 4.900 4.220 4.560
#0 BA 1.00 6.000 5.400 5.550 4.800 5.175

 

BS 93: British Association (BA) Screw Threads
Limits and Tolerances for BA External Screw Threads
Class-of-Fit = Normal; given in mm
Nominal
Size
Pitch
P

Major
Diameter

Effective/Pitch
Diameter
Minor
Diameter
Max Min Max Min Max Min
#16 BA 0.19 0.790 0.740 0.675 0.630 0.560 0.470
#15 BA 0.21 0.900 0.845 0.775 0.730 0.650 0.560
#14 BA 0.23 1.000 0.940 0.860 0.810 0.720 0.625
#13 BA 0.25 1.200 1.135 1.050 1.000 0.900 0.800
#12 BA 0.28 1.300 1.230 1.130 1.075 0.960 0.855
#11 BA 0.31 1.500 1.420 1.315 1.260 1.130 1.020
#10 BA 0.35 1.675 1.605 1.465 1.505 1.255 1.135
#9 BA 0.39 1.875 1.795 1.640 1.575 1.405 1.275
#8 BA 0.43 2.175 2.090 1.915 1.845 1.655 1.520
#7 BA 0.48 2.475 2.380 2.185 2.110 1.895 1.750
#6 BA 0.53 2.775 2.670 2.455 2.375 2.135 1.980
#5 BA 0.59 3.175 3.055 2.820 2.735 2.465 2.295
#4 BA 0.66 3.575 3.445 3.180 3.090 2.785 2.605
#3 BA 0.73 4.075 3.930 3.635 3.575 3.195 3.000
#2 BA 0.81 4.675 4.151 4.190 4.085 3.705 3.495
#1 BA 0.90 5.275 5.095 4.735 4.600 4.195 3.965
#0 BA 1.00 5.975 5.775 5.375 5.250 4.775 4.525

 

BS 93: British Association (BA) Screw Threads
Limits and Tolerances for BA External Screw Threads
Class-of-Fit = Close; given in mm
Nominal
Size
Pitch
P

Major
Diameter

Effective/Pitch
Diameter
Minor
Diameter
d Max Min d2 Max Min d1 Max Min
#10 BA 0.35 1.700 1.645 1.490 1.440 1.280 1.185
#9 BA 0.39 1.900 1.840 1.665 1.615 1.430 1.330
#8 BA 0.43 2.200 2.135 1.940 1.885 1.680 1.570
#7 BA 0.48 2.500 2.430 2.210 2.150 1.920 1.805
#6 BA 0.53 2.800 2.720 2.480 2.420 2.160 2.035
#5 BA 0.59 3.200 3.110 2.845 2.775 2.490 2.355
#4 BA 0.66 3.600 3.500 3.205 3.130 2.810 2.665
#3 BA 0.73 4.100 3.990 3.660 3.580 3.220 3.065
#2 BA 0.81 4.700 4.580 4.215 4.130 3.730 3.560
#1 BA 0.90 5.300 5.165 4.760 4.670 4.220 4.035
#0 BA 1.00 6.000 5.850 5.400 5.300 4.800 4.600

 

BS 93 Screw Thread Symbols per BS 6528
D = major diameter of internal thread
D1 = minor diameter of internal thread
D2 = effective/pitch diameter of internal thread<
d = major diameter of external thread
d1 = minor diameter of external thread
d2 = effective/pitch diameter of external thread
H = height of fundamental triangle
P = pitch

Disclaimer
This data is provided for general information only. The intention is to provide accurate information; regardless; errors may exist in the supplied information. If accuracy is critical, base your final decisions on the data provided in the root document: BS 93 (this data was taken from BS 93:2008); which is a copyrighted document. To purchase a copy visit an Authorized Reseller.

Comments:
Original Posting: 2/28/2008
Last Revision: 2/12/2013
Error corrections in, or comments about, the above data can be sent to: gageguy@gagecrib.com

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