What are partially-threaded screws?

A partially-threaded screw has a smooth shank underneath its head and threads running along the rest of the screw’s body.

Partially-threaded screws are used in applications where two pieces of material must be joined together very tightly. The top material is pulled along the smooth shank on the screw and clamped to the base material.

These types of screws do not require a clearance hole but they may still require a pilot hole.

There is another type of partially-threaded screw that has a smooth shank in the centre of the body, and threads either side.

These types of threads are usually found on decking screws. Compared to screws that have the smooth shank at the top, these screws clamp materials together extremely tightly, as the threads above the smooth shank lock the top material in place.

These types of screws may require a clearance or pilot hole.