All screws are designed with external threads so that t […]
All screws are designed with external threads so that they can be driven into objects or surfaces. On the shaft of a typical screw, you will see helical grooves. These grooves are called external threads and essentially dig material out of the object or surface into which the screw is inserted. However, not all screws have a full thread. Partially threaded and fully threaded screws are available.
What is a full-threaded screw?
A fully threaded screw is a type of fastener that features a full male thread on the shaft—also called a shank—and a pointed point.
Fully threaded screws have three basic parts: head, shaft, and tip. The head is the top of the screw, enabling the use of a specific type of screwdriver head, while the tip is the tip of the screw. Of course, the shaft is the long body of the screw that contains the external thread. In a fully threaded screw, the shaft is completely covered by the external thread.
What is a partially threaded screw?
As you may have guessed, a partially threaded screw is a type of fastener that is characterized by only partially external threads on the shaft. Like other screws, it still has a pointed tip, which is used to drive the screw into an object or surface. However, the shaft is not completely covered by the male thread.
Partially threaded screws consist of four basic parts: head, unthreaded shaft, threaded shaft, and tip. An unthreaded shaft is the portion directly below the head that does not contain threads. It is not uncommon for partially threaded screws to have one-quarter of the shaft smooth, while the remaining three-quarters have external threads. The smooth part of the shaft without threads is called the unthreaded shaft. Only some threaded screws have unthreaded shafts. Fully threaded screws have a full external thread on the shaft.
You may wonder why some screws are designed to be only partially threaded. Well, the lack of full threading allows a higher level of security for connection objects. For example, if you are trying to attach a sheet of plywood to a 2×4, you may need to use partially threaded screws. Since the threads are on the bottom of the screw, they will only remain in the 2×4, basically "grabbing" it. At the same time, the partially threaded screws will pull the plywood and 2×4 together for a stronger, more secure fix.