The British Standard Coarse Screw thread is known as a parallel screw thread of Whitworth form having a 55 degree included angle. With the standardization of Unified threads, the BSW Whitworth thread form is typically being utilized for replacement parts. Steel bolts of ¾ inch and below should not be made to close class limits and instead should be specified to medium class.

Part No: RG-310

Supplied by Rok International Industry Co., Limited

Standard: BS84.1956
BSW

Whitworth thread sizes

Major diameter		Thread pitch		Minor diameter		75% tap drill size
(in)	(mm)	(in−1)	(mm)	(in)	(mm)	(in)	(mm)
1⁄16	1.588	60	0.423	0.0412	1.046	#56	1.2
3⁄32	2.381	48	0.529	0.0671	1.704	#49	1.9
1⁄8	3.175	40	0.635	0.0930	2.362	#39	2.6
5⁄32	3.969	32	0.794	0.1162	2.951	#30	3.2
3⁄16	4.763	24	1.058	0.1341	3.406	#26	3.7
7⁄32	5.556	24	1.058	0.1654	4.201	#16	4.5
1⁄4	6.350	20	1.270	0.1860	4.724	#9	5.1
5⁄16	7.938	18	1.411	0.2414	6.132	F	6.6
3⁄8	9.525	16	1.588	0.2950	7.493	5⁄16	8.0
7⁄16	11.113	14	1.814	0.3460	8.788	U	9.4
1⁄2	12.700	12	2.117	0.3933	9.990	27⁄64	10.7
9⁄16	14.288	12	2.117	0.4558	11.577	31⁄64	12.3
5⁄8	15.875	11	2.309	0.5086	12.918	17⁄32	13.7
11⁄16	17.463	11	2.309	0.5711	14.506	19⁄32	15.2
3⁄4	19.050	10	2.540	0.6219	15.796	21⁄32	16.6
13⁄16	20.638	10	2.540	0.6844	17.384	23⁄32	18.2
7⁄8	22.225	9	2.822	0.7327	18.611	49⁄64	19.5
15⁄16	23.813	9	2.822	0.7952	20.198	53⁄64	21.1
1	25.400	8	3.175	0.8399	21.333	7⁄8	22.3
1 1⁄8	28.575	7	3.629	0.9420	23.927	63⁄64	25.1
1 1⁄4	31.750	7	3.629	1.0670	27.102	1 7⁄64	28.3
1 3⁄8	34.925	6	4.233	1.1616	29.505	1 7⁄32	30.9
1 1⁄2	38.100	6	4.233	1.2866	32.680	1 5⁄16	34.0
1 5⁄8	41.275	5	5.080	1.3689	34.770	1 7⁄16	36.4
1 3⁄4	44.450	5	5.080	1.4939	37.945	1 9⁄16	39.6
1 7⁄8	47.625	4 1⁄2	5.644	1.5904	40.396	1 5⁄8	42.2
2	50.800	4 1⁄2	5.644	1.7154	43.571	1 3⁄4	45.4
2 1⁄8	53.975	4 1⁄2	5.644	1.8404	46.746	1 7⁄8	48.6
2 1⁄4	57.150	4	6.350	1.9298	49.017	2	51.1
2 3⁄8	60.325	4	6.350	2.0548	52.192	2 1⁄8	54.2
2 1⁄2	63.500	4	6.350	2.1798	55.367	2 1⁄4	57.4
2 5⁄8	66.675	4	6.350	2.3048	58.542	2 3⁄8	60.6
2 3⁄4	69.850	3 1⁄2	7.257	2.3841	60.556	2 1⁄2	62.9
2 7⁄8	73.025	3 1⁄2	7.257	2.5091	63.731	2 5⁄8	66.1
3	76.200	3 1⁄2	7.257	2.6341	66.906	2 3⁄4	69.2
3 1⁄4	82.550	3 1⁄4	7.815	2.8560	72.542	3	75.0
3 1⁄2	88.900	3 1⁄4	7.815	3.1060	78.892	3 1⁄4	81.4
3 3⁄4	95.250	3	8.467	3.3231	84.407	3 3⁄8	87.1
4	101.600	3	8.467	3.5731	90.757	3 5⁄8	93.5
4 1⁄4	107.950	2 7⁄8	8.835	3.8046	96.637	3 7⁄8	99.5
4 1⁄2	114.300	2 7⁄8	8.835	4.0546	102.987	4 1⁄8	105.8
4 3⁄4	120.650	2 3⁄4	9.236	4.2843	108.821	4 3⁄8	111.8
5	127.000	2 3⁄4	9.236	4.5343	115.171	4 5⁄8	118.1
5 1⁄4	133.350	2 5⁄8	9.676	4.7621	120.957	4 7⁄8	124.1
5 1⁄2	139.700	2 5⁄8	9.676	5.0121	127.307	5 1⁄8	130.4
5 3⁄4	146.050	2 1⁄2	10.160	5.2377	133.038	5 3⁄8	136.3
6	152.400	2 1⁄2	10.160	5.4877	139.388	5 5⁄8	142.6