Thread pitch and size of small starter nut
Another method of determining thread pitch is less exact, but will work when no thread pitch gauge is available. You measure ¼" on the threaded portion of the bolt and then count the number of threads covered by that area. Then, you multiply by four to determine the number of threads per inch.
If you can measure the stud, that the nut screws on, it will have the same thread pitch.
If you can measure the stud, that the nut screws on, it will have the same thread pitch.
Another helpful chart:
TABLE OF BOLT SIZES/THREAD PITCH-UNIFIED NATIONAL COARSE (UNC) AND UNIFIED NATIONAL FINE (UNF)
Size-Fractional (decimal) Threads UNC Threads (UNF)
1/4" (.250") 20 28
5/16" (.3125") 18 24
3/8" (.375") 16 24
7/16" (.4375") 14 20
1/2" (.500") 13 20
9/16" (.5625") 12 18
5/8" (.625") 11 18
3/4" (.750") 10 16
TABLE OF BOLT SIZES/THREAD PITCH-UNIFIED NATIONAL COARSE (UNC) AND UNIFIED NATIONAL FINE (UNF)
Size-Fractional (decimal) Threads UNC Threads (UNF)
1/4" (.250") 20 28
5/16" (.3125") 18 24
3/8" (.375") 16 24
7/16" (.4375") 14 20
1/2" (.500") 13 20
9/16" (.5625") 12 18
5/8" (.625") 11 18
3/4" (.750") 10 16
