Tap Drill Size Chart

18 mm Drill Size

metric drill

18 mm 0.7087 in 18.00 mm

A 18 mm drill is the standard tap drill for M20 x 2.

What a 18 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 18 mm drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread % thread Chart drill Chart %
M20 x 2 chart drill 77.0% 18 mm 77.0%
3/4-20 63.6% 45/64″ 72.2%
M20 x 2.5 61.6% 17.5 mm 77.0%
3/4-16 50.9% 11/16″ 77.0%

Drills either side

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18 mm drill: common questions

What size is a 18 mm drill?
0.7087 inches, which is 18.00 mm. It is a metric drill.
What can I tap with a 18 mm drill?
4 threads: M20 x 2 at 77.0%, 3/4-20 at 63.6%, M20 x 2.5 at 61.6%, 3/4-16 at 50.9%.
Is a 18 mm drill the standard tap drill for anything?
Yes, for M20 x 2 (77.0% thread). That is the size published tap and drill charts give.
What drill is next to a 18 mm?
Down: 17.9 mm at 0.7047 in. Up: 18.1 mm at 0.7126 in.