The UNC designation 1/4-20 signifies what characteristic?

The UNC designation 1/4-20 signifies what characteristic?

• A. 1 inch diameter with 20 threads per inch
• B. 20 threads per inch for 1/4 diameter
• C. 1/4 inch diameter with 20 threads per inch
• D. 2 threads per inch for 1/4 diameter

Answer: (C)

In thread designations, the numbers tell you size and pitch. The first value is the nominal diameter in inches, and the second value is how many threads fit in one inch. The UNC part means it’s the standard coarse thread series. So 1/4-20 means a major diameter of 1/4 inch with 20 threads per inch. That corresponds to a thread pitch of 1/20 inch (0.050 in) per thread. The length or other features aren’t shown in this code. The designation identifies a quarter-inch bolt with a 20 TPI coarse thread.

In thread designations, the numbers tell you size and pitch. The first value is the nominal diameter in inches, and the second value is how many threads fit in one inch. The UNC part means it’s the standard coarse thread series. So 1/4-20 means a major diameter of 1/4 inch with 20 threads per inch. That corresponds to a thread pitch of 1/20 inch (0.050 in) per thread. The length or other features aren’t shown in this code. The designation identifies a quarter-inch bolt with a 20 TPI coarse thread.