3/8-16 UNC Thread Specs
Standard: ASME B1.1 (UNC)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 3/8-16 UNC unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.375 inches (9.52 mm) with a pitch of 0.0625 inches (TPI of 16).
For general engineering or fastening, the standard recommended tap drill is 0.3125 inches (7.94 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
3/8-16 UNC
Major Diameter (Nominal)
0.375 in(9.52 mm)
TPI (Threads per Inch)
16
Pitch
0.0625 in
Pitch Diameter
0.3344 in(8.49 mm)
Minor Diameter (Ext)
0.3073 in(7.81 mm)
Minor Diameter (Int)
0.3141 in(7.98 mm)
Thread Height
0.0541 in
Drilling & Strength Specs
Tap Drill Size
0.3125 in(7.94 mm)
Stress Area
0.0775 in²(49.99 mm²)
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Frequently Asked Questions
What is the tap drill size for 3/8-16 UNC?
The recommended tap drill size for a 3/8-16 UNC thread is 0.3125 inches (approx. 7.94 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 3/8-16 UNC bolt have?
A standard 3/8-16 UNC thread has exactly 16 threads per inch (TPI), with a corresponding linear pitch of 0.0625 inches.
What is the major diameter of a 3/8-16 UNC thread in millimeters?
The nominal major diameter of a 3/8-16 UNC thread is 0.375 inches, which converts to 9.52 mm.