Common Counterbore Sizes
STANDARD 1/64 OVERSIZE 1/32 OVERSIZE
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PILOT BODY PILOT BODY PILOT BODY
4-40 .113 .186 4-40 .126 .202 4-40 .144 .216
5-40 .125 .207 5-40 .140 .222 5-40 .1563 .239
6-32 .140 .229 6-32 .156 .246 6-32 .173 .260
8-32 .166 .272 8-32 .182 .287 8-32 .190 .305
10-32 .191 .317 10-32 .209 .331 10-32 .221 .346
1/4 .250 .381 1/4 .265 .396 1/4 .281 .415
5/16 .312 .477 5/16 .328 .490 5/16 .343 .500
3/8 .375 .596 3/8 .390 .590 3/8 .406 .605
7/16 .437 .662 7/16 .453 .677 7/16 .468 .692
1/2 .500 .758 1/2 .515 .773 1/2 .531 .790