#10-24 UNC thread pitch and dimensions

The #10-24 UNC thread has 24 threads per inch, a pitch of 0.0417 in (1.06 mm), on a 0.190 in major diameter (ASME B1.1). Its basic pitch diameter is 0.1629 in and its basic minor diameter is 0.1449 in.

Threads per inch (UNC)

24 TPI

pitch 0.0417 in · 1.06 mm

Major diameter (D)

0.190 in (4.83 mm)

Pitch (1 / TPI)

0.0417 in (1.06 mm)

Basic pitch diameter (E)

0.1629 in (4.14 mm)

Basic minor diameter (internal)

0.1449 in (3.68 mm)

Tensile stress area (As)

0.0175 in² (11.3 mm²)

Tap drill (75% chart)

#25 (0.1495 in)

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#10-24 UNC basic dimensions (ASME B1.1)
Dimension	Formula	inch	mm
Major diameter D	nominal	0.1900	4.83
Pitch P	1 / TPI	0.0417	1.06
Pitch diameter E	D − 0.649519 / n	0.1629	4.14
Minor diameter (internal)	D − 1.082532 / n	0.1449	3.68
Thread height (basic)	0.541266 / n	0.0226	0.57
Tensile stress area As	0.7854 (D − 0.9743 / n)²	0.0175 in²	11.3 mm²

#10 threads: UNC vs UNF
Thread	TPI	Pitch Ø E	Stress area As	Tap drill
#10-24 UNC (this page)	24	0.1629 in	0.0175 in²	#25
#10-32 UNF	32	0.1697 in	0.0200 in²	#21

Neighbouring UNC threads
Thread	TPI	Pitch (mm)	Minor Ø	Stress area As
#6-32 UNC	32	0.79	0.1042 in	0.0091 in²
#8-32 UNC	32	0.79	0.1302 in	0.0140 in²
#10-24 UNC (this page)	24	1.06	0.1449 in	0.0175 in²
1/4-20 UNC	20	1.27	0.1959 in	0.0318 in²
5/16-18 UNC	18	1.41	0.2524 in	0.0524 in²

Practical notes

Unified threads are named diameter–TPI–series: #10-24 UNC is a #10 nominal diameter (number 10 screw, 0.190 in) with 24 threads per inch in the coarse series.

These are basic (zero-tolerance) dimensions. Most screws are made to class 2A and nuts to 2B (ASME B1.1), so measured sizes sit slightly below the basic values on the screw.

24 TPI is a pitch of 1.06 mm, which does not match a metric ISO pitch exactly; metric and Unified fasteners of similar size are not interchangeable.

Tensile stress area As is the area used for bolt strength (proof load = As × proof stress for the SAE J429 or ASTM grade). For #10-24 UNC it is 0.0175 in².

FAQ

How many threads per inch is #10-24 UNC?

24 TPI, a pitch of 0.0417 in (1.06 mm), in the Unified coarse series (ASME B1.1).

What is the minor diameter of #10-24 UNC?

The basic minor diameter of the internal thread is D − 1.082532/n = 0.1449 in (3.68 mm).

What is the tensile stress area of #10-24 UNC?

As = 0.7854 × (D − 0.9743/n)² = 0.0175 in² (11.3 mm²).

What tap drill does #10-24 UNC need?

The standard chart drill is #25, 0.1495 in (3.8 mm), about 75% thread.

What is the difference between #10-24 UNC and #10-32 UNF?

Same #10 diameter, different pitch: 24 TPI versus 32 TPI. They are not interchangeable.

Sources: ASME B1.1 — Unified inch screw threads (UN and UNR thread form): basic dimensions, tensile stress area · ASME B18.2.1 — square, hex, heavy hex and askew head bolts and hex, heavy hex, hex flange screws (width across flats)

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