3/4-20 UNEF Thread Specs
Standard: ASME B1.1 (UNEF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 3/4-20 UNEF unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 0.75 inches (19.05 mm) with a pitch of 0.05 inches (TPI of 20).
For general engineering or fastening, the standard recommended tap drill is 0.7 inches (17.78 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
3/4-20 UNEF
Major Diameter (Nominal)
0.75 in(19.05 mm)
TPI (Threads per Inch)
20
Pitch
0.05 in
Pitch Diameter
0.7175 in(18.23 mm)
Minor Diameter (Ext)
0.6959 in(17.68 mm)
Minor Diameter (Int)
0.7013 in(17.81 mm)
Thread Height
0.0433 in
Drilling & Strength Specs
Tap Drill Size
0.7 in(17.78 mm)
Stress Area
0.3863 in²(249.2 mm²)
Quick Unit Converter
mm
⇄
inch
Frequently Asked Questions
What is the tap drill size for 3/4-20 UNEF?
The recommended tap drill size for a 3/4-20 UNEF thread is 0.7 inches (approx. 17.78 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 3/4-20 UNEF bolt have?
A standard 3/4-20 UNEF thread has exactly 20 threads per inch (TPI), with a corresponding linear pitch of 0.05 inches.
What is the major diameter of a 3/4-20 UNEF thread in millimeters?
The nominal major diameter of a 3/4-20 UNEF thread is 0.75 inches, which converts to 19.05 mm.