1"-20 UNEF Thread Specs
Standard: ASME B1.1 (UNEF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 1"-20 UNEF unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 1 inches (25.4 mm) with a pitch of 0.05 inches (TPI of 20).
For general engineering or fastening, the standard recommended tap drill is 0.95 inches (24.13 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
1"-20 UNEF
Major Diameter (Nominal)
1 in(25.4 mm)
TPI (Threads per Inch)
20
Pitch
0.05 in
Pitch Diameter
0.9675 in(24.58 mm)
Minor Diameter (Ext)
0.9459 in(24.03 mm)
Minor Diameter (Int)
0.9513 in(24.16 mm)
Thread Height
0.0433 in
Drilling & Strength Specs
Tap Drill Size
0.95 in(24.13 mm)
Stress Area
0.7107 in²(458.54 mm²)
Quick Unit Converter
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Frequently Asked Questions
What is the tap drill size for 1"-20 UNEF?
The recommended tap drill size for a 1"-20 UNEF thread is 0.95 inches (approx. 24.13 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 1"-20 UNEF bolt have?
A standard 1"-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 1"-20 UNEF thread in millimeters?
The nominal major diameter of a 1"-20 UNEF thread is 1 inches, which converts to 25.4 mm.