Round Head Screw Style - The Thelen Channel

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Machine Screw Head Dimensions

Round Head

The round head has a semi-eliptical top surface and a flat bearing surface. This head was the most used style in the past. It is being replaced with other type heads in newer designs but it is sometimes preferred for its smooth surface and appearance.
This table references ANSI B18.6.3

Nominal Size	A		H		J		T		M		G	N	Phillips Driver Size
	Head Diameter		Height of Head		Slot Width		Slot Depth		Dimensions of Recess
	Head Diameter		Height of Head		Slot Width		Slot Depth		Diameter		Depth	Width
	Max	Min	Max	Min	Max	Min	Max	Min	Max	Min	Max	Min
2	.162	.146	.069	.059	.031	.023	.048	.037	.100	.087	.053	.017	1
3	.187	.169	.078	.067	.035	.027	.053	.040	.109	.096	.062	.018	1
4	.211	.193	.086	.075	.039	.031	.058	.044	.118	.105	.072	.019	1
5	.236	.217	.095	.083	.043	.035	.063	.047	.154	.141	.074	.027	2
6	.260	.240	.103	.091	.048	.039	.068	.051	.162	.149	.084	.027	2
8	.309	.287	.120	.107	.054	.045	.077	.058	.178	.165	.101	.030	2
10	.359	.334	.137	.123	.060	.050	.087	.065	.195	.182	.119	.031	2
12	.408	.382	.153	.139	.067	.056	.096	.073	.249	.236	.125	.032	3
1/4	.472	.443	.175	.160	.075	.064	.109	.082	.268	.255	.147	.034	3
5/16	.590	.557	.216	.198	.084	.072	.132	.099	.308	.295	.187	.040	3
3/8	.708	.670	.256	.237	.094	.081	.155	.117	.387	.374	.228	.064	4
1/2	.813	.766	.355	.332	.106	.091	.211	.159	.416	.403	.256	.068	4

This page was last updated 04/24/06 10:42 AM 1957