What are coarse-threaded screws
and fine-threaded screws?

Screws are either coarse-threaded or fine-threaded.

Coarse-threaded screws have a greater pitch (more space between each thread).

Fine-threaded screws have a smaller pitch (less space between each thread).

Coarse-threaded screws

Compared to fine-threaded screws, coarse-threaded ones takes less time to insert or remove. This is because the screw travels further in one rotation due to the greater space between threads.

Coarse-threaded screws are less likely to jam if the screw is inserted at an angle.

Coarse-threaded screws are used in softer materials such as soft/hard wood, plastic or plasterboard. This is because their threads are able to grip the soft fibres of the material and hold the screw in place.

A fine-threaded screw would be more likely to slip out of soft material.

Coarse threads with serrated edges

The coarse threads on some screws have sharp serrated edges. Manufacturers claim that this allows the threads to cut more easily through the fibres of the material.

Screws with serrated threads tend to be more expensive.

Fine-threaded screws

Compared to coarse-threaded screws, fine-threaded ones takes more time to insert or remove. This is because the screw does not travel as far in one rotation due to the smaller space between threads.

Because a fine-threaded screw takes longer to insert or remove, it allows for finer adjustment when working.

Screws with fine threads are used in harder materials such as metal and are usually inserted into a tapped hole.Their fine threads allow them to be secured extremely tightly in hard materials.

A coarse-threaded screw would not be able to clamp two hard materials together because of the large gap between each thread.