Whitworth's Standard Screw Threads for Bolts

Dia of Bolt		No of Threads per Inch.	Diameter at bottom of Thread	Distance Across Flat	Distances Across Corners	Thickness of Bolt Head	Thickness of Nut
Fractional Sizes	Decimal Sizes
	0.25	20	0.1860	0.525	0.6062	0.2187
	0.3125	18	0.2414	0.6014	0.6944	0.2734
	0.375	16	0.2950	0.7094	0.8191	0.3281
	0.4375	14	0.3460	0.8204	0.9473	0.3828
	0.5	12	0.3933	0.9191	1.0612	0.4375
	0.5625	12	0.4558	1.011	1.1674	0.4921
	0.625	11	0.5086	1.101	1.2713	0.5468
	0.6875	11	0.5711	1.2011	1.3869	0.6015
	0.75	10	0.6219	1.3012	1.5024	0.6562
	0.8125	10	0.6844	1.39	1.6050	0.7109
	0.875	9	0.7327	1.4788	1.7075	0.7656
1	1.0	8	0.8399	1.6701	1.9284	0.875	1
	1.125	7	0.9420	1.8605	2.1483	0.9843
	1.25	7	1.0670	2.0483	2.3651	1.0937
	1.375	6	1.1616	2.2146	2.5571	1.2031
	1.5	6	1.2866	2.4134	2.7867	1.3125
	1.625	5	1.3689	2.5763	2.9748	1.4218
	1.75	5	1.4939	2.7578	3.1844	1.5312
2	2.0	4.5	1.7154	3.1491	3.6362	1.75	2
	2.25	4	1.9298	3.546	4.0945	1.9687
	2.5	4	2.1798	3.894	4.4964	2.1875
	2.75	3.5	2.3841	4.181	4.8278	2.4062
3	3.0	3.5	2.6341	4.531	5.2319	2.625	3
	3.25	3.25	2.8560	4.85	5.6002	2.843
	3.5	3.25	3.1060	5.175	5.9755	3.062
	3.75	3	3.3231	5.55	6.4085	3.281
4	4.0	3	3.5731	5.95	6.8704	3.5	4
	4.5	2.875	4.0546	6.825	7.8819	3.937
5	5.0	2.75	4.5343	7.8	9.0066	4.375	5
	5.5	2.625	5.0121	8.85	10.2190	4.812
6	6.0	2.5	5.4877	10	11.5470	5.25	6

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