1-1/8-12 UNF Thread Specs
Standard: ASME B1.1 (UNF)
Find the technical dimensions, threads per inch (TPI), and tapping guidelines for the 1-1/8-12 UNF unified thread.
Compliant with the ASME B1.1 standard, this size has a nominal major diameter of 1.125 inches (28.58 mm) with a pitch of 0.08333 inches (TPI of 12).
For general engineering or fastening, the standard recommended tap drill is 1.0417 inches (26.46 mm) to achieve adequate thread engagement.
Dimensional Specifications (Inches & mm)
Size Designation
1-1/8-12 UNF
Major Diameter (Nominal)
1.125 in(28.58 mm)
TPI (Threads per Inch)
12
Pitch
0.08333 in
Pitch Diameter
1.0709 in(27.2 mm)
Minor Diameter (Ext)
1.0348 in(26.28 mm)
Minor Diameter (Int)
1.0438 in(26.51 mm)
Thread Height
0.0722 in
Drilling & Strength Specs
Tap Drill Size
1.0417 in(26.46 mm)
Stress Area
0.8557 in²(552.08 mm²)
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Frequently Asked Questions
What is the tap drill size for 1-1/8-12 UNF?
The recommended tap drill size for a 1-1/8-12 UNF thread is 1.0417 inches (approx. 26.46 mm) to achieve standard thread engagement.
How many threads per inch (TPI) does a 1-1/8-12 UNF bolt have?
A standard 1-1/8-12 UNF thread has exactly 12 threads per inch (TPI), with a corresponding linear pitch of 0.08333 inches.
What is the major diameter of a 1-1/8-12 UNF thread in millimeters?
The nominal major diameter of a 1-1/8-12 UNF thread is 1.125 inches, which converts to 28.58 mm.