F Drill Size

letter drill

F 0.257 in 6.53 mm

A F drill is the standard tap drill for 5/16-18.

What a F drill taps

Every thread this drill cuts between 50% and 85% of thread, deepest first. Outside that band it is the wrong drill for the job, so nothing below that line is listed.

Threads a F drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
5/16-18 chart drill	76.9%	F	76.9%

Drills either side

E 0.250 in · 6.35 mm Next size down
G 0.261 in · 6.63 mm Next size up

All drill sizes → · Open this drill in the calculator →

F drill: common questions

What size is a F drill?

0.257 inches, which is 6.53 mm. It is a letter drill.

What can I tap with a F drill?

1 thread: 5/16-18 at 76.9%.

Is a F drill the standard tap drill for anything?

Yes, for 5/16-18 (76.9% thread). That is the size published tap and drill charts give.

What drill is next to a F?

Down: E at 0.250 in. Up: G at 0.261 in.