5/16-24 UNF Thread Specs
Standard: ASME B1.1 (UNF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 5/16-24 UNF unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.3125 inches (7.94 mm) with a pitch of 0.04167 inches (TPI of 24).
For general engineering or fastening, the standard recommended tap drill is 0.2708 inches (6.88 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
5/16-24 UNF
Major Diameter (Nominal)
0.3125 in(7.94 mm)
TPI (Threads per Inch)
24
Pitch
0.04167 in
Pitch Diameter
0.2854 in(7.25 mm)
Minor Diameter (Ext)
0.2674 in(6.79 mm)
Minor Diameter (Int)
0.2719 in(6.91 mm)
Thread Height
0.0361 in
Drilling & Strength Specs
Tap Drill Size
0.2708 in(6.88 mm)
Stress Area
0.0581 in²(37.46 mm²)
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Frequently Asked Questions
What is the tap drill size for 5/16-24 UNF?
The recommended tap drill size for a 5/16-24 UNF thread is 0.2708 inches (approx. 6.88 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 5/16-24 UNF bolt have?
A standard 5/16-24 UNF thread has exactly 24 threads per inch (TPI), with a corresponding linear pitch of 0.04167 inches.
What is the major diameter of a 5/16-24 UNF thread in millimeters?
The nominal major diameter of a 5/16-24 UNF thread is 0.3125 inches, which converts to 7.94 mm.