#27 Drill Size

number drill

#27 0.144 in 3.66 mm

A #27 drill measures 0.144 in. It taps 2 threads in this chart.

What a #27 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 #27 drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
#10-24	85.0%	#25	74.8%
#8-36	55.4%	#29	77.6%

Other jobs for a #27

Hard-material tap drill: The size to use in stainless or tool steel for #8-36, where it leaves a shallower thread than the standard drill and cuts tapping torque.
Clearance hole: The through hole a bolt passes in, not a tapped hole: loose fit for #4-40, loose fit for #4-48. See the clearance hole chart.

Drills either side

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

#27 drill: common questions

What size is a #27 drill?

0.144 inches, which is 3.66 mm. It is a number drill.

What can I tap with a #27 drill?

2 threads: #10-24 at 85.0%, #8-36 at 55.4%.

Is a #27 drill used for clearance holes?

Yes: loose fit for #4-40, loose fit for #4-48. A clearance hole is not tapped; the bolt passes through it.

What drill is next to a #27?

Down: 3.6 mm at 0.1417 in. Up: 3.7 mm at 0.1457 in.