K Drill Size

letter drill

K 0.281 in 7.14 mm

A K drill measures 0.281 in. It taps 4 threads in this chart.

What a K 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 K drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
5/16-32	77.6%	9/32″	77.1%
M8 x 1	66.4%	7 mm	77.0%
5/16-24	58.2%	I	74.8%
M8 x 1.25	53.1%	6.8 mm	73.9%

Other jobs for a K

Hard-material tap drill: The size to use in stainless or tool steel for 5/16-24, where it leaves a shallower thread than the standard drill and cuts tapping torque.

Drills either side

7.1 mm 0.2795 in · 7.1 mm Next size down
9/32″ 0.2812 in · 7.14 mm Next size up

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

K drill: common questions

What size is a K drill?

0.281 inches, which is 7.14 mm. It is a letter drill.

What can I tap with a K drill?

4 threads: 5/16-32 at 77.6%, M8 x 1 at 66.4%, 5/16-24 at 58.2%, M8 x 1.25 at 53.1%.

What drill is next to a K?

Down: 7.1 mm at 0.2795 in. Up: 9/32 in at 0.2812 in.