#12-24 UNC Thread Specs
Standard: ASME B1.1 (UNC)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the #12-24 UNC unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.216 inches (5.49 mm) with a pitch of 0.04167 inches (TPI of 24).
For general engineering or fastening, the standard recommended tap drill is 0.1743 inches (4.43 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
#12-24 UNC
Major Diameter (Nominal)
0.216 in(5.49 mm)
TPI (Threads per Inch)
24
Pitch
0.04167 in
Pitch Diameter
0.1889 in(4.8 mm)
Minor Diameter (Ext)
0.1709 in(4.34 mm)
Minor Diameter (Int)
0.1754 in(4.46 mm)
Thread Height
0.0361 in
Drilling & Strength Specs
Tap Drill Size
0.1743 in(4.43 mm)
Stress Area
0.0242 in²(15.59 mm²)
Quick Unit Converter
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Frequently Asked Questions
What is the tap drill size for #12-24 UNC?
The recommended tap drill size for a #12-24 UNC thread is 0.1743 inches (approx. 4.43 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a #12-24 UNC bolt have?
A standard #12-24 UNC thread has exactly 24 threads per inch (TPI), with a corresponding linear pitch of 0.04167 inches.
What is the major diameter of a #12-24 UNC thread in millimeters?
The nominal major diameter of a #12-24 UNC thread is 0.216 inches, which converts to 5.49 mm.