Tap Drill Size Chart

W Drill Size

letter drill

W 0.386 in 9.80 mm

A W drill measures 0.386 in. It taps 2 threads in this chart.

What a W 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 W drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread % thread Chart drill Chart %
7/16-20 79.3% 25/64″ 72.2%
7/16-14 55.5% U 74.9%

Other jobs for a W

Hard-material tap drill
The size to use in stainless or tool steel for 7/16-14, where it leaves a shallower thread than the standard drill and cuts tapping torque.

Drills either side

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

W drill: common questions

What size is a W drill?
0.386 inches, which is 9.80 mm. It is a letter drill.
What can I tap with a W drill?
2 threads: 7/16-20 at 79.3%, 7/16-14 at 55.5%.
What drill is next to a W?
Down: 9.8 mm at 0.3858 in. Up: 9.9 mm at 0.3898 in.