1/2-28 UNEF Thread Specs
Standard: ASME B1.1 (UNEF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 1/2-28 UNEF 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 0.03571 inches (TPI of 28).
For general engineering or fastening, the standard recommended tap drill is 0.4643 inches (11.79 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
1/2-28 UNEF
Major Diameter (Nominal)
0.5 in(12.7 mm)
TPI (Threads per Inch)
28
Pitch
0.03571 in
Pitch Diameter
0.4768 in(12.11 mm)
Minor Diameter (Ext)
0.4613 in(11.72 mm)
Minor Diameter (Int)
0.4652 in(11.82 mm)
Thread Height
0.0309 in
Drilling & Strength Specs
Tap Drill Size
0.4643 in(11.79 mm)
Stress Area
0.17 in²(109.66 mm²)
Quick Unit Converter
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Frequently Asked Questions
What is the tap drill size for 1/2-28 UNEF?
The recommended tap drill size for a 1/2-28 UNEF thread is 0.4643 inches (approx. 11.79 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 1/2-28 UNEF bolt have?
A standard 1/2-28 UNEF thread has exactly 28 threads per inch (TPI), with a corresponding linear pitch of 0.03571 inches.
What is the major diameter of a 1/2-28 UNEF thread in millimeters?
The nominal major diameter of a 1/2-28 UNEF thread is 0.5 inches, which converts to 12.7 mm.