1-1/8 in Drill Size

fractional drill

1-1/8″ 1.125 in 28.58 mm

A 1-1/8 in drill measures 1.125 in. It taps 3 threads in this chart.

What a 1-1/8 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 1-1/8 in drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
M30 x 1.5	73.1%	28.5 mm	77.0%
1-1/4-7	67.4%	1-7/64″	75.8%
M30 x 2	54.8%	28 mm	77.0%

Drills either side

28.5 mm 1.122 in · 28.5 mm Next size down
1-9/64″ 1.1406 in · 28.97 mm Next size up

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

1-1/8 in drill: common questions

What size is a 1-1/8 in drill?

1.125 inches, which is 28.58 mm. It is a fractional drill.

What can I tap with a 1-1/8 in drill?

3 threads: M30 x 1.5 at 73.1%, 1-1/4-7 at 67.4%, M30 x 2 at 54.8%.

What drill is next to a 1-1/8 in?

Down: 28.5 mm at 1.122 in. Up: 1-9/64 in at 1.1406 in.