BS 93 British Association (B.A.) Screw Threads

BS 93 British Association (BA) Screw Threads Data Charts

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: office@gagecrib.com