What drill for a 7/16-20 roll (form) tap?

About 0.4154 in; the nearest standard drill is Z. Check your tap maker's table.

What drill for a 7/16-20 Helicoil?

Drill 31/64" (0.4844 in), then tap with the 7/16-20 STI tap.

7/16-20 tap drill size

Use a W drill (0.3860 in) for a 7/16-20 cutting tap at 75% thread.

Drills for 7/16-20 (UNF)
Tap type	Drill	Decimal (in)
Cutting tap, 75% thread	W	0.3860
Cutting tap, 50% thread (hard material)	X	0.3970
Roll / form tap, 65% thread	Z	0.4130
Helicoil / STI insert (7/16-20×1D)	31/64"	0.4844

Pitch: 1.27 mm (20 TPI)
Major Ø: 0.4375
Pitch Ø: 0.4050
Minor Ø: 0.3762

Open the tap drill calculator Roll tap chart Helicoil chart

Common questions

What size drill for a 7/16-20 tap?: Use a W drill (0.3860 in) for a 7/16-20 cutting tap at 75% thread.
What drill for a 7/16-20 roll (form) tap?: About 0.4154 in; the nearest standard drill is Z. Check your tap maker's table.
What drill for a 7/16-20 Helicoil?: Drill 31/64" (0.4844 in), then tap with the 7/16-20 STI tap.

Other UNF sizes

Drill sizes from Machinery's Handbook and ASME B1.1/B1.13M; roll tap sizes from the form-tap formula. Tap and insert makers' tables are authoritative.