#3-56 UNF Thread Specs
Standard: ASME B1.1 (UNF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the #3-56 UNF unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.099 inches (2.51 mm) with a pitch of 0.01786 inches (TPI of 56).
For general engineering or fastening, the standard recommended tap drill is 0.0811 inches (2.06 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
#3-56 UNF
Major Diameter (Nominal)
0.099 in(2.51 mm)
TPI (Threads per Inch)
56
Pitch
0.01786 in
Pitch Diameter
0.0874 in(2.22 mm)
Minor Diameter (Ext)
0.0797 in(2.02 mm)
Minor Diameter (Int)
0.0816 in(2.07 mm)
Thread Height
0.0155 in
Drilling & Strength Specs
Tap Drill Size
0.0811 in(2.06 mm)
Stress Area
0.0052 in²(3.37 mm²)
Quick Unit Converter
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Frequently Asked Questions
What is the tap drill size for #3-56 UNF?
The recommended tap drill size for a #3-56 UNF thread is 0.0811 inches (approx. 2.06 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a #3-56 UNF bolt have?
A standard #3-56 UNF thread has exactly 56 threads per inch (TPI), with a corresponding linear pitch of 0.01786 inches.
What is the major diameter of a #3-56 UNF thread in millimeters?
The nominal major diameter of a #3-56 UNF thread is 0.099 inches, which converts to 2.51 mm.