7/8-14 UNF Thread Specs
Standard: ASME B1.1 (UNF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 7/8-14 UNF unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.875 inches (22.23 mm) with a pitch of 0.07143 inches (TPI of 14).
For general engineering or fastening, the standard recommended tap drill is 0.8036 inches (20.41 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
7/8-14 UNF
Major Diameter (Nominal)
0.875 in(22.23 mm)
TPI (Threads per Inch)
14
Pitch
0.07143 in
Pitch Diameter
0.8286 in(21.05 mm)
Minor Diameter (Ext)
0.7977 in(20.26 mm)
Minor Diameter (Int)
0.8054 in(20.46 mm)
Thread Height
0.0619 in
Drilling & Strength Specs
Tap Drill Size
0.8036 in(20.41 mm)
Stress Area
0.5095 in²(328.69 mm²)
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Frequently Asked Questions
What is the tap drill size for 7/8-14 UNF?
The recommended tap drill size for a 7/8-14 UNF thread is 0.8036 inches (approx. 20.41 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 7/8-14 UNF bolt have?
A standard 7/8-14 UNF thread has exactly 14 threads per inch (TPI), with a corresponding linear pitch of 0.07143 inches.
What is the major diameter of a 7/8-14 UNF thread in millimeters?
The nominal major diameter of a 7/8-14 UNF thread is 0.875 inches, which converts to 22.23 mm.