ASME B18.3 Hexagon Socket And Spline Socket Button Head Cap Screws

ASME B18.3 Hexagon Socket And Spline Socket Button Head Cap Screws Standard covers complete general and dimensional data for hexagon and spline socket head cap screws recognized as an American National Standard. Also included are appendices that provide specifications for hexagon socket gages and gaging, tables showing applicability of keys and bits to these screws, drill and counterbore sizes for socket head cap screws, and formulas used for dimensional data. However, where questions arise concerning acceptance of product, the dimensions in the tables shall govern over recalculation by formula. Recess dimensions for Type VI recesses are given in Mandatory Appendix III.

Nominal Size	Shoulder Diameter		Head Diameter		Head Height		Head Side Height	Head Side Height	Thread Length	Thread Neck Diameter		Thread Neck Width	Shoulder Neck Dia.	Shoulder Neck Width	Thread Neck Fillet		Head Fillet Extension Above D	Hexagon Socket Size
	Max.	Min.	Max.	Min.	Max.	Min.	Min.	Size	Length	Max.	Min.	Max.	Min.	Max.	Max.	Min.	Max.	Nom.
	D		A		H		S	D₁	E	G		I	K	F	N		M	J
ASME B18.3 - 1⁄4	0.248	0.246	0.375	0.357	0.188	0.177	0.157	10-24	0.375	0.142	0.133	0.083	0.227	0.093	0.023	0.017	0.014	1⁄8
ASME B18.3 - 5⁄16	0.3105	0.3085	0.438	0.419	0.219	0.209	0.183	1⁄4 -20	0.438	0.193	0.182	0.1	0.289	0.093	0.028	0.022	0.017	5⁄32
ASME B18.3 - 3⁄8	0.373	0.371	0.562	0.543	0.25	0.24	0.209	5⁄1 6-18	0.5	0.249	0.237	0.111	0.352	0.093	0.031	0.025	0.02	3⁄16
ASME B18.3 - 1⁄2	0.498	0.496	0.75	0.729	0.312	0.302	0.262	3⁄8 -16	0.625	0.304	0.291	0.125	0.477	0.093	0.035	0.029	0.026	1⁄4
ASME B18.3 - 5⁄8	0.623	0.621	0.875	0.853	0.375	0.365	0.315	1⁄2 -13	0.75	0.414	0.397	0.154	0.602	0.093	0.042	0.036	0.032	5⁄16
ASME B18.3 - 3⁄4	0.748	0.746	1	0.977	0.5	0.49	0.421	5⁄8 -11	0.875	0.521	0.502	0.182	0.727	0.093	0.051	0.045	0.039	3⁄8
ASME B18.3 - 1	0.998	0.996	1.312	1.287	0.625	0.61	0.527	3⁄4 -10	1	0.638	0.616	0.2	0.977	0.125	0.055	0.049	0.05	1⁄2
ASME B18.3 - 1 1⁄4	1.248	1.246	1.75	1.723	0.75	0.735	0.633	7⁄8 -9	1.125	0.75	0.726	0.222	1.227	0.125	0.062	0.056	0.06	5⁄8
ASME B18.3 - 1 1⁄2	1.498	1.496	2.125	2.095	1	0.98	0.842	1 1⁄8-7	1.5	0.964	0.934	0.286	1.478	0.125	0.072	0.066	0.07	7⁄8
ASME B18.3 - 1 3⁄4	1.748	1.746	2.375	2.345	1.125	1.105	0.948	1 1⁄4-7	1.75	1.089	1.059	0.286	1.728	0.125	0.072	0.066	0.08	1
ASME B18.3 - 2	1.998	1.996	2.75	2.72	1.25	1.23	1.054	1 1⁄2-6	2	1.307	1.277	0.333	1.978	0.125	0.102	0.096	0.09	1 1⁄4
All dimensions in inches. The body of the screw is the unthreaded cylindrical portion of the shank where not threaded to the head; the shank being the portion of the screw from the point of juncture of the conical bearing surface and the body to the flat of the point. The length of thread LT is the distance measured from the extreme point to the last complete (full form) thread. Standard length increments of No. 0 through 1-inch sizes are as follows: 1 ⁄ 16 inch for nominal screw lengths of 1 ⁄ 8 through 1 ⁄ 4 inch; 1 ⁄ 8 inch for lengths of 1 ⁄ 4 through 1 inch; 1 ⁄ 4 inch for lengths of 1 inch through 3 1 ⁄ 2 inches; 1 ⁄ 2 inch for lengths of 3 1 ⁄ 2 through 7 inches; and 1 inch for lengths of 7 through 10 inches, incl. For screw sizes over 1 inch, length increments are: 1 ⁄ 2 inch for nominal screw lengths of 1 inch through 7 inches; 1 inch for lengths of 7 through 10 inches; and 2 inches for lengths over 10 inches. Threads shall be Unified external threads with radius root; Class 3A UNRC and UNRF series for sizes No. 0 through 1 inch and Class 2A UNRC and UNRF series for sizes over 1 inch to 1 1 ⁄ 2 inches, incl. For manufacturing details not shown, including materials, see American National Standard ASME B18.3-1998 Socket dimensions.

ASME Material Specifications

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