What drill for a 5/8-24 roll (form) tap?

About 0.6066 in; the nearest standard drill is 39/64. Check your tap maker's table.

5/8-24 tap drill size

Use a 37/64 drill (0.5781 in) for a 5/8-24 cutting tap at 75% thread.

Drills for 5/8-24 (UNEF)
Tap type	Drill	Decimal (in)
Cutting tap, 75% thread	37/64	0.5781
Cutting tap, 50% thread (hard material)	19/32	0.5938
Roll / form tap, 65% thread	39/64	0.6094

Pitch: 1.0583 mm (24 TPI)
Major Ø: 0.6250
Pitch Ø: 0.5979
Minor Ø: 0.5799

5/8-24 tapping speeds and feeds

Feed = pitch (0.0417 in per rev). Starting points for a general-purpose HSS cut tap:

Aluminum 6061 / 7075: 430 RPM · 17.9 IPM
Free-machining / mild steel: 120 RPM · 5.00 IPM
304 / 316 stainless: 60 RPM · 2.50 IPM

Tap speeds and feeds by size · 37/64 drill size and speeds

Open the tap drill calculator Roll tap chart Helicoil chart

Common questions

What size drill for a 5/8-24 tap?: Use a 37/64 drill (0.5781 in) for a 5/8-24 cutting tap at 75% thread.
What drill for a 5/8-24 roll (form) tap?: About 0.6066 in; the nearest standard drill is 39/64. Check your tap maker's table.

Other UNEF 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.

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