Which class of screw thread features the most threads per inch for a particular size?

The class of screw thread that features the most threads per inch for a particular size is Unified national fine. This type of threading offers a finer pitch than its coarse counterpart, meaning there are more threads within the same section of length. The finer threads provide several advantages, including a greater potential for precision and tighter clamping, which can be beneficial in applications requiring a higher degree of accuracy or fine adjustments.

Unified national fine threads are commonly used in situations where strong clamping force and minimal backlash are essential, making them preferable in mechanical and engineering applications. In comparison, coarse threads tend to have fewer threads per inch, which makes them more suitable for quick assembly and disassembly, but they may not provide the same level of precision as fine threads.