WHITWORTH SCREW THREAD

Diagram of the Whitworth screw thread

Abbreviations:

P = Pitch in mm.	N = Number of threads per inch.
H = Height.	r = Radius
D = Depth.	DE = Screw Diameter.
DM = Mid Diameter.	DF = Interior Diameter.

Formulas and Calculator:

Whitworth thread sizes table

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
11⁄8	28.575	7	3.629	0.9420	23.927	63⁄64	25.1
11⁄4	31.750	7	3.629	1.0670	27.102	17⁄64	28.3
13⁄8	34.925	6	4.233	1.1616	29.505	17⁄32	30.9
11⁄2	38.100	6	4.233	1.2866	32.680	15⁄16	34.0
15⁄8	41.275	5	5.080	1.3689	34.770	17⁄16	36.4
13⁄4	44.450	5	5.080	1.4939	37.945	19⁄16	39.6
17⁄8	47.625	41⁄2	5.644	1.5904	40.396	15⁄8	42.2
2	50.800	41⁄2	5.644	1.7154	43.571	13⁄4	45.4
21⁄8	53.975	41⁄2	5.644	1.8404	46.746	17⁄8	48.6
21⁄4	57.150	4	6.350	1.9298	49.017	2	51.1
23⁄8	60.325	4	6.350	2.0548	52.192	21⁄8	54.2
21⁄2	63.500	4	6.350	2.1798	55.367	21⁄4	57.4
25⁄8	66.675	4	6.350	2.3048	58.542	23⁄8	60.6
23⁄4	69.850	31⁄2	7.257	2.3841	60.556	21⁄2	62.9
27⁄8	73.025	31⁄2	7.257	2.5091	63.731	25⁄8	66.1
3	76.200	31⁄2	7.257	2.6341	66.906	23⁄4	69.2
31⁄4	82.550	31⁄4	7.815	2.8560	72.542	3	75.0
31⁄2	88.900	31⁄4	7.815	3.1060	78.892	31⁄4	81.4
33⁄4	95.250	3	8.467	3.3231	84.407	33⁄8	87.1
4	101.600	3	8.467	3.5731	90.757	35⁄8	93.5
41⁄4	107.950	27⁄8	8.835	3.8046	96.637	37⁄8	99.5
41⁄2	114.300	27⁄8	8.835	4.0546	102.987	41⁄8	105.8
43⁄4	120.650	23⁄4	9.236	4.2843	108.821	43⁄8	111.8
5	127.000	23⁄4	9.236	4.5343	115.171	45⁄8	118.1
51⁄4	133.350	25⁄8	9.676	4.7621	120.957	47⁄8	124.1
51⁄2	139.700	25⁄8	9.676	5.0121	127.307	51⁄8	130.4
53⁄4	146.050	21⁄2	10.160	5.2377	133.038	53⁄8	136.3
6	152.400	21⁄2	10.160	5.4877	139.388	55⁄8	142.6

Hex head sizes table

Size	BS 190		BS 1083		DIN
(in)	(in)	(mm)	(in)	(mm)	(mm)
1⁄8	0.344	8.7	—	—	—
3⁄16	0.445	11.3	—	—	—
1⁄4	0.525	13.3	0.445	11.3	11
5⁄16	0.600	15.2	0.525	13.3	14
3⁄8	0.710	18.0	0.600	15.2	17
7⁄16	0.820	20.8	0.710	18.0	19
1⁄2	0.920	23.4	0.820	20.8	22
9⁄16	1.010	25.7	0.920	23.4	—
5⁄8	1.100	27.9	1.010	25.7	27
3⁄4	1.300	33.0	1.200	30.5	32
7⁄8	1.480	37.6	1.300	33.0	36
1	1.670	42.4	1.480	37.6	41
11⁄8	1.860	47.2	1.670	42.4	—
11⁄4	2.050	52.1	1.860	47.2	—
13⁄8	—	—	2.050	52.1	—
11⁄2	2.410	61.2	2.220	56.4	—
13⁄4	2.760	70.1	2.580	65.5	—
2	3.150	80.0	2.760	70.1	—

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