UNC — Unified coarse

#6-32 UNC

Tap drill #36 for a #6-32 UNC thread — major Ø 3.505 mm, pitch 0.794 mm (32 TPI).

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Tap drill

#36

2.71 mm · ≈78% thread

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Thread form & key diameters

Dimensions

Designation	#6-32 UNC
Major (outside) diameter	3.505 mm · 0.138"
Pitch	0.794 mm · 32 TPI
Pitch diameter	2.99 mm · 0.1177"
Minor diameter (external)	2.531 mm · 0.0997"
Minor diameter (internal)	2.646 mm · 0.1042"
Recommended tap drill	#36 · 2.71 mm · ≈78% thread
Clearance hole	Close #23 · Normal #18 · Loose #7 — nominal + 1/64" / 1/32" / 1/16" to the nearest standard drill (common shop practice).
Socket key (across flats)	7/64"

Close #23 · Normal #18 · Loose #7 — nominal + 1/64" / 1/32" / 1/16" to the nearest standard drill (common shop practice).

What tap drill do I need for #6-32 UNC?

For a #6-32 UNC thread, drill the hole with a #36 tap drill (2.71 mm) before tapping. That produces roughly 78% thread engagement, the usual target for a strong, tappable hole. The mating bolt has a major diameter of 3.505 mm and a pitch of 0.794 mm (32 TPI).

To pass a #6-32 UNC bolt through a part rather than thread it, use a clearance hole: Close #23 · Normal #18 · Loose #7 — nominal + 1/64" / 1/32" / 1/16" to the nearest standard drill (common shop practice)..

All values are generated from the standard thread formulas (ISO 68-1 / ASME B1.1) and published standard tables — not hand-entered. See the full reference.

Same diameter

Other #6 threads

M3.5 × 0.6Tap 2.9 mmØ 3.5 mm · pitch 0.6 mm #6-40 UNFTap #33Ø 3.505 mm · pitch 0.635 mm

Nearby sizes

More unc — unified coarse threads

#5-40 UNCTap #38Ø 3.175 mm · pitch 0.635 mm #4-40 UNCTap #43Ø 2.845 mm · pitch 0.635 mm #8-32 UNCTap #29Ø 4.166 mm · pitch 0.794 mm #3-48 UNCTap #47Ø 2.515 mm · pitch 0.529 mm #2-56 UNCTap #50Ø 2.184 mm · pitch 0.454 mm #10-24 UNCTap #25Ø 4.826 mm · pitch 1.058 mm #1-64 UNCTap #53Ø 1.854 mm · pitch 0.397 mm #12-24 UNCTap #16Ø 5.486 mm · pitch 1.058 mm