How to measure the thread
The pitch is the distance from the crest of one thread to the next in mm. TPI (Threads per inch) is used by inch thread
Otherwise known as UNC Unified National Coarse
standard threads (coarse thread)
UNC meaning Unified Coarse, is the most dominant used in the USA. Often used in the agricultural industry because of their strong coarse threads. Generally available in steel and stainless steel. Come in higher grades – high tensile and higher grades available.
Otherwise known as UNF Unified National Fine
UNF meaning Unified Fine, also a dominant thread in the USA. Often used in the automobile industry because of their tight fine threads. Generally available in steel and stainless steel. Come in higher grades – high tensile and higher grades available
Fine threads are commonly used for nuts and bolts in high strength applications. While applications vary, in general, fine threads are approximately 10% stronger than coarse threads.
Otherwise known as UNEF Unified National Extra Fine.
UNEF (Unified Extra Fine) is the same as UNF except that the number of threads per inch is even higher for each fastener size.