What drill for a 1-72 roll (form) tap?

About 0.0669 in; the nearest standard drill is #51. Check your tap maker's table.

What drill for a 1-72 Helicoil?

Drill #45 (0.0820 in), then tap with the 1-72 STI tap.

1-72 tap drill size

Use a #53 drill (0.0595 in) for a 1-72 cutting tap at 75% thread.

Drills for 1-72 (UNF)
Tap type	Drill	Decimal (in)
Cutting tap, 75% thread	#53	0.0595
Cutting tap, 50% thread (hard material)	#52	0.0635
Roll / form tap, 65% thread	#51	0.0670
Helicoil / STI insert (#1-72×1D)	#45	0.0820

Pitch: 0.3528 mm (72 TPI)
Major Ø: 0.0730
Pitch Ø: 0.0640
Minor Ø: 0.0560

Open the tap drill calculator Roll tap chart Helicoil chart

Common questions

What size drill for a 1-72 tap?: Use a #53 drill (0.0595 in) for a 1-72 cutting tap at 75% thread.
What drill for a 1-72 roll (form) tap?: About 0.0669 in; the nearest standard drill is #51. Check your tap maker's table.
What drill for a 1-72 Helicoil?: Drill #45 (0.0820 in), then tap with the 1-72 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.