Free Table of Recommended Drill Sizes

Self-Tapping Screw Size			Major Thread Diameter			Minor Thread Diameter			For Heavy Metals		For Light Metals
No.	Threads per Inch	O.D.	Max.	Mean	Min.	Max.	Mean	Min.	Drill Size		Drill Size
2	32	.086	.088	.0850	.082	.064	.0620	.060	49	.0730	49	.0730
4	24	.112	.114	.1110	.108	.086	.0840	.082	41	.0960	41	.0960
5	20	.125	.130	.1265	.123	.094	.0920	.090	36	.1065	36	.1065
6	20	.138	.139	.1355	.132	.104	.1015	.099	32	.1160	32	.1160
7	19	.151	.154	.1505	.147	.115	.1120	.109	30	.1285	30	.1285
8	18	.164	.166	.1625	.159	.122	.1190	.116	28	.1405	29	.1360
10	16	.190	.189	.1855	.182	.141	.1380	.135	20	.1610	21	.1590
12	14	.216	.215	.2115	.208	.164	.1605	.157	13	.1850	14	.1820
1/4	14	.250	.246	.2415	.237	.192	.1885	.185	3	.2130	4	.2090
5/16	12	.313	.315	.3105	.306	.244	.2400	.236	I	.2720	H	.2660
3/8	12	.375	.380	.3755	.371	.309	.3040	.299	R	.3390	Q	.3320