1/2-20 UNF Thread Specs
Standard: ASME B1.1 (UNF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 1/2-20 UNF 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 0.05 inches (TPI of 20).
For general engineering or fastening, the standard recommended tap drill is 0.45 inches (11.43 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
1/2-20 UNF
Major Diameter (Nominal)
0.5 in(12.7 mm)
TPI (Threads per Inch)
20
Pitch
0.05 in
Pitch Diameter
0.4675 in(11.88 mm)
Minor Diameter (Ext)
0.4459 in(11.33 mm)
Minor Diameter (Int)
0.4513 in(11.46 mm)
Thread Height
0.0433 in
Drilling & Strength Specs
Tap Drill Size
0.45 in(11.43 mm)
Stress Area
0.16 in²(103.2 mm²)
Quick Unit Converter
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Frequently Asked Questions
What is the tap drill size for 1/2-20 UNF?
The recommended tap drill size for a 1/2-20 UNF thread is 0.45 inches (approx. 11.43 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 1/2-20 UNF bolt have?
A standard 1/2-20 UNF thread has exactly 20 threads per inch (TPI), with a corresponding linear pitch of 0.05 inches.
What is the major diameter of a 1/2-20 UNF thread in millimeters?
The nominal major diameter of a 1/2-20 UNF thread is 0.5 inches, which converts to 12.7 mm.