#28 Drill Size

number drill

#28 0.1405 in 3.57 mm

A #28 drill measures 0.1405 in. It taps 2 threads in this chart.

What a #28 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 #28 drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
#8-36	65.1%	#29	77.6%
#8-32	57.9%	#29	69.0%

Other jobs for a #28

Hard-material tap drill: The size to use in stainless or tool steel for #8-32, where it leaves a shallower thread than the standard drill and cuts tapping torque.

Drills either side

3.5 mm 0.1378 in · 3.5 mm Next size down
9/64″ 0.1406 in · 3.57 mm Next size up

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

#28 drill: common questions

What size is a #28 drill?

0.1405 inches, which is 3.57 mm. It is a number drill.

What can I tap with a #28 drill?

2 threads: #8-36 at 65.1%, #8-32 at 57.9%.

What drill is next to a #28?

Down: 3.5 mm at 0.1378 in. Up: 9/64 in at 0.1406 in.