Compared to standard threads, a fine thread has a smaller pitch which increases the resilience. It is used e.g. for adjusting screws in measuring instruments because it allows for finer settings. The term consists of the letter M, the nominal diameter and the pitch, the flank angle is 60°.
UNC - Unified Coarse Thread. The old definition NC is comparable with the metric thread. The new term UNC is comparable with the ISO metric thread. NC and UNC threads are interchangeable, in an analogous manner like the metric and the ISO metric thread. The flank angle is 60°