1/2-13 UNC Thread Specs
Standard: ASME B1.1 (UNC)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 1/2-13 UNC unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.5 inches (12.7 mm) with a pitch of 0.07692 inches (TPI of 13).
For general engineering or fastening, the standard recommended tap drill is 0.4231 inches (10.75 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
1/2-13 UNC
Major Diameter (Nominal)
0.5 in(12.7 mm)
TPI (Threads per Inch)
13
Pitch
0.07692 in
Pitch Diameter
0.45 in(11.43 mm)
Minor Diameter (Ext)
0.4167 in(10.58 mm)
Minor Diameter (Int)
0.4251 in(10.8 mm)
Thread Height
0.0666 in
Drilling & Strength Specs
Tap Drill Size
0.4231 in(10.75 mm)
Stress Area
0.1419 in²(91.55 mm²)
Quick Unit Converter
mm
⇄
inch
Frequently Asked Questions
What is the tap drill size for 1/2-13 UNC?
The recommended tap drill size for a 1/2-13 UNC thread is 0.4231 inches (approx. 10.75 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 1/2-13 UNC bolt have?
A standard 1/2-13 UNC thread has exactly 13 threads per inch (TPI), with a corresponding linear pitch of 0.07692 inches.
What is the major diameter of a 1/2-13 UNC thread in millimeters?
The nominal major diameter of a 1/2-13 UNC thread is 0.5 inches, which converts to 12.7 mm.