55/64 in Drill Size

fractional drill

55/64″ 0.8594 in 21.83 mm

A 55/64 in drill measures 0.8594 in. It taps 2 threads in this chart.

What a 55/64 in 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 55/64 in drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
M24 x 2	83.6%	22 mm	77.0%
M24 x 3	55.7%	21 mm	77.0%

Other jobs for a 55/64 in

Form-tap hole: The published roll-tap hole for 7/8-20. A form tap displaces metal instead of cutting it, so it needs this larger hole.

Drills either side

53/64″ 0.8281 in · 21.03 mm Next size down
22 mm 0.8661 in · 22 mm Next size up

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

55/64 in drill: common questions

What size is a 55/64 in drill?

0.8594 inches, which is 21.83 mm. It is a fractional drill.

What can I tap with a 55/64 in drill?

2 threads: M24 x 2 at 83.6%, M24 x 3 at 55.7%.

What drill is next to a 55/64 in?

Down: 53/64 in at 0.8281 in. Up: 22 mm at 0.8661 in.