G Drill Size

letter drill

G 0.261 in 6.63 mm

A G drill measures 0.261 in. It taps 2 threads in this chart.

What a G 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 G drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
M8 x 1.25	84.4%	6.8 mm	73.9%
5/16-18	71.4%	F	76.9%

Drills either side

F 0.257 in · 6.53 mm Next size down
6.7 mm 0.2638 in · 6.7 mm Next size up

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

G drill: common questions

What size is a G drill?

0.261 inches, which is 6.63 mm. It is a letter drill.

What can I tap with a G drill?

2 threads: M8 x 1.25 at 84.4%, 5/16-18 at 71.4%.

What drill is next to a G?

Down: F at 0.257 in. Up: 6.7 mm at 0.2638 in.