The thread series symbol in a Unified thread designation indicates the specific type and characteristics of the thread. This symbol helps identify the thread’s design and intended application. Common thread series symbols include:
- UN: Unified , the general series used for both coarse and fine threads.
- UNR: Unified , requires rounded root.
- UNC: Unified Coarse, designed for applications where a more robust and easier-to-machine thread is preferred. It has fewer threads per inch compared to fine threads, providing greater strength and better resistance to stripping.
- UNF: Unified Fine, intended for applications requiring a higher number of threads per inch. This series offers finer threads that are useful for precision adjustments and higher load capacities in smaller thread sizes.
- UNEF: Unified Extra Fine, used for applications needing very fine threads for tighter tolerance and precision.
- UNS: Unified Stub, featuring a shorter thread profile to provide increased strength in specific applications.
Each of these symbols specifies the thread’s series, which dictates the thread’s pitch and the overall thread form, helping to ensure that threaded components are compatible and perform as intended.
