#12-28 UNF Thread Specs
Standard: ASME B1.1 (UNF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the #12-28 UNF unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.216 inches (5.49 mm) with a pitch of 0.03571 inches (TPI of 28).
For general engineering or fastening, the standard recommended tap drill is 0.1803 inches (4.58 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
#12-28 UNF
Major Diameter (Nominal)
0.216 in(5.49 mm)
TPI (Threads per Inch)
28
Pitch
0.03571 in
Pitch Diameter
0.1928 in(4.9 mm)
Minor Diameter (Ext)
0.1773 in(4.5 mm)
Minor Diameter (Int)
0.1812 in(4.6 mm)
Thread Height
0.0309 in
Drilling & Strength Specs
Tap Drill Size
0.1803 in(4.58 mm)
Stress Area
0.0258 in²(16.64 mm²)
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Frequently Asked Questions
What is the tap drill size for #12-28 UNF?
The recommended tap drill size for a #12-28 UNF thread is 0.1803 inches (approx. 4.58 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a #12-28 UNF bolt have?
A standard #12-28 UNF thread has exactly 28 threads per inch (TPI), with a corresponding linear pitch of 0.03571 inches.
What is the major diameter of a #12-28 UNF thread in millimeters?
The nominal major diameter of a #12-28 UNF thread is 0.216 inches, which converts to 5.49 mm.