R Drill Size

letter drill

R 0.339 in 8.61 mm

A R drill measures 0.339 in. It taps 2 threads in this chart.

What a R 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 R drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
M10 x 1.5	71.3%	8.5 mm	77.0%
3/8-24	66.5%	Q	79.4%

Drills either side

8.6 mm 0.3386 in · 8.6 mm Next size down
8.7 mm 0.3425 in · 8.7 mm Next size up

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

R drill: common questions

What size is a R drill?

0.339 inches, which is 8.61 mm. It is a letter drill.

What can I tap with a R drill?

2 threads: M10 x 1.5 at 71.3%, 3/8-24 at 66.5%.

What drill is next to a R?

Down: 8.6 mm at 0.3386 in. Up: 8.7 mm at 0.3425 in.