S Drill Size

letter drill

S 0.348 in 8.84 mm

A S drill measures 0.348 in. It taps 3 threads in this chart.

What a S 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 S drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
M10 x 1.25	71.5%	8.8 mm	73.9%
3/8-32	66.5%	11/32″	76.9%
M10 x 1.5	59.6%	8.5 mm	77.0%

Other jobs for a S

Hard-material tap drill: The size to use in stainless or tool steel for 3/8-32, where it leaves a shallower thread than the standard drill and cuts tapping torque.
Form-tap hole: The published roll-tap hole for 3/8-16. A form tap displaces metal instead of cutting it, so it needs this larger hole.

Drills either side

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

S drill: common questions

What size is a S drill?

0.348 inches, which is 8.84 mm. It is a letter drill.

What can I tap with a S drill?

3 threads: M10 x 1.25 at 71.5%, 3/8-32 at 66.5%, M10 x 1.5 at 59.6%.

What drill is next to a S?

Down: 8.8 mm at 0.3465 in. Up: 8.9 mm at 0.3504 in.