Thread Class 1A, 2A, 3A

Thread classes 1A, 2A, and 3A are classifications of the Unified National Coarse (UNC) and Unified National Fine (UNF) thread standards in the United States. These classes are mainly used to measure thread size tolerance and the fit between threads.

Thread class 1A is generally used for general applications with looser tolerances and lower size accuracy, but it is convenient to use and relatively inexpensive.

Thread class 2A is a medium-grade class with smaller tolerances and higher size accuracy, which is usually used in applications with higher requirements such as automobiles, airplanes, etc.

Thread class 3A is the highest class of thread with very small tolerances and high size accuracy. It is mainly used in high-end machinery and instruments, such as precision instruments, aerospace equipment, etc.

In summary, the difference between thread classes 1A, 2A, and 3A lies in the tolerance and usage range. By selecting different grades of threads, different application requirements can be met.