BS 1083 Precision Hexagon Screws

Nominal Size D	Number of Threads per Inch		Width			Diameter of Washer Face G		Radius Under Head R		Thickness
	Number of Threads per Inch		Across Flats A		Across Corners C	Diameter of Washer Face G		Radius Under Head R		Head F
	BSW	BSF	Max.	Min. ^a	Max.	Max.	Min.	Max.	Min.	Max.	Min.
BS 1083 - 1⁄4	20	26	0.445	0.438	0.51	0.428	0.418	0.025	0.015	0.176	0.166
BS 1083 - 5⁄16	18	22	0.525	0.518	0.61	0.508	0.498	0.025	0.015	0.218	0.208
BS 1083 - 3⁄8	16	20	0.6	0.592	0.69	0.582	0.572	0.025	0.015	0.26	0.25
BS 1083 - 7⁄16	14	18	0.71	0.702	0.82	0.69	0.68	0.025	0.015	0.302	0.292
BS 1083 - 1⁄2	12	16	0.82	0.812	0.95	0.8	0.79	0.025	0.015	0.343	0.333
BS 1083 - 9⁄16	12	16	0.92	0.912	1.06	0.9	0.89	0.045	0.02	0.375	0.365
BS 1083 - 5⁄8	11	14	1.01	1	1.17	0.985	0.975	0.045	0.02	0.417	0.407
BS 1083 - 3⁄4	10	12	1.2	1.19	1.39	1.175	1.165	0.045	0.02	0.5	0.48
BS 1083 - 7⁄8	9	11	1.3	1.288	1.5	1.273	1.263	0.065	0.04	0.583	0.563
BS 1083 - 1	8	10	1.48	1.468	1.71	1.453	1.443	0.095	0.06	0.666	0.636
BS 1083 - 11⁄8	7	9	1.67	1.64	1.93	1.62	1.61	0.095	0.06	0.75	0.71
BS 1083 - 11⁄4	7	9	1.86	1.815	2.15	1.795	1.785	0.095	0.06	0.83	0.79
BS 1083 - 13⁄8b	…	8	2.05	2.005	2.37	1.985	1.975	0.095	0.06	0.92	0.88
BS 1083 - 11⁄2	6	8	2.22	2.175	2.56	2.155	2.145	0.095	0.06	1	0.96
BS 1083 - 13⁄4	5	7	2.58	2.52	2.98	2.495	2.485	0.095	0.06	1.17	1.11
BS 1083 - 2	5	7	2.76	2.7	3.19	2.675	2.665	0.095	0.06	1.33	1.27
a When bolts from 1⁄4 to 1 inch are hot forged, the tolerance on the width across flats shall be two and a half times the tolerance shown in the table and shall be unilaterally minus from maximum size. For dimensional notation, see diagram on page 1571. b Noted standard with BSW thread. All dimensions in inches except where otherwise noted.