28.5 mm Drill Size

metric drill

28.5 mm 1.122 in 28.50 mm

A 28.5 mm drill is the standard tap drill for M30 x 1.5.

What a 28.5 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 28.5 mm 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 chart drill	77.0%	28.5 mm	77.0%
1-1/4-7	69.0%	1-7/64″	75.8%
M30 x 2	57.7%	28 mm	77.0%

Other jobs for a 28.5 mm

Hard-material tap drill: The size to use in stainless or tool steel for M30 x 2, where it leaves a shallower thread than the standard drill and cuts tapping torque.
Form-tap hole: The published roll-tap hole for M30 x 3.5. A form tap displaces metal instead of cutting it, so it needs this larger hole.

Drills either side

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28.5 mm drill: common questions

What size is a 28.5 mm drill?

1.122 inches, which is 28.50 mm. It is a metric drill.

What can I tap with a 28.5 mm drill?

3 threads: M30 x 1.5 at 77.0%, 1-1/4-7 at 69.0%, M30 x 2 at 57.7%.

Is a 28.5 mm drill the standard tap drill for anything?

Yes, for M30 x 1.5 (77.0% thread). That is the size published tap and drill charts give.

What drill is next to a 28.5 mm?

Down: 1-7/64 in at 1.1094 in. Up: 1-1/8 in at 1.125 in.