2"-4.5 UNC Thread Specs
Standard: ASME B1.1 (UNC)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 2"-4.5 UNC unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 2 inches (50.8 mm) with a pitch of 0.22222 inches (TPI of 4.5).
For general engineering or fastening, the standard recommended tap drill is 1.7778 inches (45.16 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
2"-4.5 UNC
Major Diameter (Nominal)
2 in(50.8 mm)
TPI (Threads per Inch)
4.5
Pitch
0.22222 in
Pitch Diameter
1.8557 in(47.13 mm)
Minor Diameter (Ext)
1.7594 in(44.69 mm)
Minor Diameter (Int)
1.7835 in(45.3 mm)
Thread Height
0.1925 in
Drilling & Strength Specs
Tap Drill Size
1.7778 in(45.16 mm)
Stress Area
2.4982 in²(1611.75 mm²)
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Frequently Asked Questions
What is the tap drill size for 2"-4.5 UNC?
The recommended tap drill size for a 2"-4.5 UNC thread is 1.7778 inches (approx. 45.16 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 2"-4.5 UNC bolt have?
A standard 2"-4.5 UNC thread has exactly 4.5 threads per inch (TPI), with a corresponding linear pitch of 0.22222 inches.
What is the major diameter of a 2"-4.5 UNC thread in millimeters?
The nominal major diameter of a 2"-4.5 UNC thread is 2 inches, which converts to 50.8 mm.