You can’t ignore the thread type when choosing fasteners. Fasteners like screws and bolts have external threads. External threads are helical ridges on the outside of a fastener. They feature a spiral-like design that wraps around the fastener’s shank. While some fasteners have coarse threads, though, others have fine threads.

Coarse vs Fine Threads Explained

The threads on fasteners can be categorized as either coarse or fine depending on size. Coarse threads are wide, whereas fine threads are narrow. Coarse threads are also typically deeper than fine threads.

Fasteners with coarse threads have fewer ridges than those with fine threads. Coarse threads are wider than fine threads, so they take up more space. As a result, fasteners with coarse threads have fewer, albeit larger, ridges than fasteners with fine threads.

You can refer to a fastener’s label to determine whether it has coarse or fine threads. UNC fasteners typically have coarse thread, whereas UNF fasteners have fine thread.