What drill for a 8-36 roll (form) tap?

About 0.1517 in; the nearest standard drill is #24. Check your tap maker's table.

What drill for a 8-36 Helicoil?

Drill #13 (0.1850 in), then tap with the 8-36 STI tap.

8-36 tap drill size

Use a #29 drill (0.1360 in) for a 8-36 cutting tap at 75% thread.

Drills for 8-36 (UNF)
Tap type	Drill	Decimal (in)
Cutting tap, 75% thread	#29	0.1360
Cutting tap, 50% thread (hard material)	#27	0.1440
Roll / form tap, 65% thread	#24	0.1520
Helicoil / STI insert (#8-36×1D)	#13	0.1850

Pitch: 0.7056 mm (36 TPI)
Major Ø: 0.1640
Pitch Ø: 0.1460
Minor Ø: 0.1299

Open the tap drill calculator Roll tap chart Helicoil chart

Common questions

What size drill for a 8-36 tap?: Use a #29 drill (0.1360 in) for a 8-36 cutting tap at 75% thread.
What drill for a 8-36 roll (form) tap?: About 0.1517 in; the nearest standard drill is #24. Check your tap maker's table.
What drill for a 8-36 Helicoil?: Drill #13 (0.1850 in), then tap with the 8-36 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.