In the Unified Thread Series, graded pitch series refer to the different classifications of thread pitches that are used to specify the coarseness or fineness of the threads. These graded pitch series help in determining the thread’s suitability for various applications and ensure compatibility between threaded components. The main graded pitch series include:
- Unified National Coarse (UNC): This series features a relatively coarse pitch, meaning fewer threads per inch. It is commonly used for general-purpose applications where strength and ease of assembly are prioritized. UNC threads are robust and are less likely to strip or cross-thread, making them suitable for many standard fastening needs.
- Unified National Fine (UNF): This series has a finer pitch, with more threads per inch compared to UNC threads. It is used in applications where greater precision and finer adjustments are required. UNF threads offer better engagement in smaller diameters and provide a higher shear strength, which is beneficial for precision machinery and tight-tolerance components.
- Unified National Extra Fine (UNEF): This series features an even finer pitch than UNF, used for applications requiring very precise threading and tight tolerances. UNEF threads are often found in specialized and high-precision applications where fine thread engagement and detailed adjustments are necessary.
