13/16-20 UNEF Thread Specs
Standard: ASME B1.1 (UNEF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 13/16-20 UNEF unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.8125 inches (20.64 mm) with a pitch of 0.05 inches (TPI of 20).
For general engineering or fastening, the standard recommended tap drill is 0.7625 inches (19.37 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
13/16-20 UNEF
Major Diameter (Nominal)
0.8125 in(20.64 mm)
TPI (Threads per Inch)
20
Pitch
0.05 in
Pitch Diameter
0.78 in(19.81 mm)
Minor Diameter (Ext)
0.7584 in(19.26 mm)
Minor Diameter (Int)
0.7638 in(19.4 mm)
Thread Height
0.0433 in
Drilling & Strength Specs
Tap Drill Size
0.7625 in(19.37 mm)
Stress Area
0.4582 in²(295.6 mm²)
Quick Unit Converter
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Frequently Asked Questions
What is the tap drill size for 13/16-20 UNEF?
The recommended tap drill size for a 13/16-20 UNEF thread is 0.7625 inches (approx. 19.37 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 13/16-20 UNEF bolt have?
A standard 13/16-20 UNEF thread has exactly 20 threads per inch (TPI), with a corresponding linear pitch of 0.05 inches.
What is the major diameter of a 13/16-20 UNEF thread in millimeters?
The nominal major diameter of a 13/16-20 UNEF thread is 0.8125 inches, which converts to 20.64 mm.