4.2 mm Drill Size

metric drill

4.2 mm 0.1654 in 4.20 mm

A 4.2 mm drill is the standard tap drill for M5 x 0.8.

What a 4.2 mm 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 4.2 mm drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
M5 x 0.8 chart drill	77.0%	4.2 mm	77.0%
#10-32	60.6%	#21	76.4%

Drills either side

4.1 mm 0.1614 in · 4.1 mm Next size down
#19 0.166 in · 4.22 mm Next size up

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

4.2 mm drill: common questions

What size is a 4.2 mm drill?

0.1654 inches, which is 4.20 mm. It is a metric drill.

What can I tap with a 4.2 mm drill?

2 threads: M5 x 0.8 at 77.0%, #10-32 at 60.6%.

Is a 4.2 mm drill the standard tap drill for anything?

Yes, for M5 x 0.8 (77.0% thread). That is the size published tap and drill charts give.

What drill is next to a 4.2 mm?

Down: 4.1 mm at 0.1614 in. Up: #19 at 0.166 in.