What does the 'NC' in 1/4-20NC signify about the bolt?

The designation 'NC' in the bolt specification 1/4-20NC indicates that the bolt is National Coarse threaded. National Coarse (NC) refers to a series of unified threads with a thread pitch that is relatively coarse, allowing for easier assembly and disassembly in applications where frequent adjustment or maintenance may be necessary. In this case, the '1/4' represents the nominal diameter of the bolt in inches, while '20' refers to the number of threads per inch.

This specification is important in various mechanical and engineering applications because coarse threads are less likely to strip and provide an adequate grip in materials like wood and plastic. Understanding this classification helps in selecting the right bolt for specific operational requirements, ensuring secure fastening and proper function in assemblies.