Z Drill Size

letter drill

Z 0.413 in 10.49 mm

A Z drill measures 0.413 in. It taps 3 threads in this chart.

What a Z 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 Z drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
M12 x 1.5	77.5%	10.5 mm	77.0%
M12 x 1.75	66.4%	10.2 mm	79.2%
7/16-28	52.8%	Y	72.2%

Other jobs for a Z

Hard-material tap drill: The size to use in stainless or tool steel for 7/16-28, where it leaves a shallower thread than the standard drill and cuts tapping torque.
Form-tap hole: The published roll-tap hole for 7/16-20. 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 →

Z drill: common questions

What size is a Z drill?

0.413 inches, which is 10.49 mm. It is a letter drill.

What can I tap with a Z drill?

3 threads: M12 x 1.5 at 77.5%, M12 x 1.75 at 66.4%, 7/16-28 at 52.8%.

What drill is next to a Z?

Down: 10.4 mm at 0.4094 in. Up: 10.5 mm at 0.4134 in.