UNC / UNF - unified national thread

The most common types of UN (Unified National) thread are:

• UNC – Unified National Coarse Thread, comparable with the ISO metric thread
• UNF – Unified National Fine Thread

*Compared to standard threads (coarse thread), fine thread has a smaller pitch.

Unified threads come in three different classes:

1A (external) & 1B (internal): for applications where a liberal tolerance is required to permit easy assembly even with slightly nicked threads.
2A (external) & 2B (internal): most commonly used class for general applications.
3A (external) & 3B (internal): for applications where closeness of fit and/or accuracy of thread elements are important.

If you have any questions please contact us or check out our fittings with UNF thread.

Flank angle is 60 °.
Female and male thread are both parallel.