#38 Drill Size: 0.1015 in / 2.58 mm

What a #38 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 #38 drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
#5-44	79.6%	#37	71.1%
#5-40 chart drill	72.4%	#38	72.4%
M3 x 0.5	65.0%	2.5 mm	77.0%

Other jobs for a #38

Form-tap hole: The published roll-tap hole for #4-40. A form tap displaces metal instead of cutting it, so it needs this larger hole.
Clearance hole: The through hole a bolt passes in, not a tapped hole: normal fit for #2-56, normal fit for #2-64. See the clearance hole chart.

Drills either side

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#38 drill: common questions

What size is a #38 drill?

0.1015 inches, which is 2.58 mm. It is a number drill.

What can I tap with a #38 drill?

3 threads: #5-44 at 79.6%, #5-40 at 72.4%, M3 x 0.5 at 65.0%.

Is a #38 drill the standard tap drill for anything?

Yes, for #5-40 (72.4% thread). That is the size published tap and drill charts give.

Is a #38 drill used for clearance holes?

Yes: normal fit for #2-56, normal fit for #2-64. A clearance hole is not tapped; the bolt passes through it.

What drill is next to a #38?

Down: 2.55 mm at 0.1004 in. Up: 2.6 mm at 0.1024 in.