Overview thread types
UNC - Unified Coarse Thread Series
American standard coarse thread. The old designation NC is comparable with the metric thread. The new designation UNC is comparable to the ISO metric thread. NC and UNC threads are interchangeable, corresponding to the metric and iso-metric threads.
UNF - Unified National Fine Thread Series = fine pitch thread.
Same design as UNC. UNC and UNF threads are the thread selection for commercial screws and nuts.