Tap Drill Size Chart

#43 Drill Size

number drill

#43 0.089 in 2.26 mm

A #43 drill is the standard tap drill for #4-40.

What a #43 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 #43 drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread % thread Chart drill Chart %
#4-48 85.0% #42 68.4%
#4-40 chart drill 70.8% #43 70.8%

Other jobs for a #43

Form-tap hole
The published roll-tap hole for #3-48, #3-56. 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 #1-64, normal fit for #1-72. See the clearance hole chart.

Drills either side

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#43 drill: common questions

What size is a #43 drill?
0.089 inches, which is 2.26 mm. It is a number drill.
What can I tap with a #43 drill?
2 threads: #4-48 at 85.0%, #4-40 at 70.8%.
Is a #43 drill the standard tap drill for anything?
Yes, for #4-40 (70.8% thread). That is the size published tap and drill charts give.
Is a #43 drill used for clearance holes?
Yes: normal fit for #1-64, normal fit for #1-72. A clearance hole is not tapped; the bolt passes through it.
What drill is next to a #43?
Down: 2.2 mm at 0.0866 in. Up: 2.3 mm at 0.0906 in.