What is the difference between UNC, UNF, UNEF, UN and UNS in thread code?

Mar 09, 2023

There are differences in tooth shape, tooth quantity and application among coarse thread (UNC), fine thread (UNF), ultra-fine thread (UNEF) and special pitch thread (UNS).

1. Dental shape

UNC represents the coarse thread of United States unified thread UN series (optional radius of external thread base). The coarse thread has a large tooth shape and a large pitch.

UNF is United Fine Thread. Fine teeth have fine teeth.

The unified thread of the UNEF superfine teeth series is smaller than that of the fine teeth. It belongs to the American standard ANSI B1.1.

The UNS special thread is a unified thread of the special series. The special thread is also called special thread. The thread has special shape, such as outer contour and tooth shape.

2, The amount of teeth

UNC has fewer teeth per unit length.

UNF more teeth per unit length.

UNEF has more teeth per unit length than fine thread.

UNS had the largest number of teeth per unit length.

3. Application

UNC is also used for connection and fastening between mechanical parts. General thread connection uses coarse thread.

UNF fine teeth are generally used where loosening is required. Fine thread into more teeth, that is, can play a role in reducing fluid leakage, so used in the need for sealing occasions. Fine thread can also play a role in fine tuning because of the advantages of small pitch.

The UNEF series is suitable for use with thin-walled tubes, thin nuts, short sleeves or short joints where short length and smaller pitch are required.

UNS offers a wide range of diameter/pitch combinations for specific design requirements that the UNC, UNF, and UNEF series cannot meet. Constant pitch series are used for parts that are reassembled and disassembled multiple times or for parts that are easy to re-thread.

UN thread is the United States, Britain, Canada and other jointly developed on the basis of inch size thread standard, called unified thread.