When specified as 1/4-28, what does the 1/4 indicate?

The designation 1/4-28 specifically categorizes a bolt's dimensions, where the 1/4 indicates the diameter of the bolt in inches. This means that the bolt has a circular cross-section with a width of one-quarter of an inch. In mechanical applications, this measurement is crucial for ensuring that the bolt properly fits into corresponding nuts, holes, or fixtures, and for assessing its load-bearing capacity. The second part of the designation, 28, refers to the number of threads per inch, which is essential for determining how tightly the bolt will engage with its counterpart. Understanding this labeling system is fundamental in fields requiring precise fastener specifications, such as electrical and mechanical engineering, which are relevant to the MTA Transit Electrical Helper role.