When inspecting a standard sheet metal screw, you may notice that it has sharp threads. All screws, of course, have threads. Consisting of helical ridges that extend fully or partially down the shank, they convert rotational force into linear force to grip the surrounding material. Sheet metal screws, however, typically have sharper threads than other types of screws.
Thread-Cutting
One of the main reasons sheet metal screws have sharp threads is because they are thread-cutting. Not to be confused with self-drilling screws, thread-cutting screws are designed to cut their own threads. When driven into an object, they will scoop out and remove material while simultaneously creating internal threads in the object.
Sheet metal screws have sharp threads so that they can easily cut into materials and create their own threads. The edges of their threads are narrow and sharp. As these sharp threads turn, they create matching grooves in the form of internal threads. This thread-cutting process eliminates the need for tapping holes, thus speeding up installation.
Improved Grip
Another reason sheet metal screws have sharp threads is to improve their grip. Sheet metal screws have a stronger grip than many other types of screws. Their sharp threads dig into materials to create a tight, secure connection.
Sheet metal screws, of course, are typically used to fasten sheet metal. The problem with sheet metal is that it doesn’t provide much material for engagement. A standard piece of sheet metal is typically less then one-tenth of an inch thick. With so little material, it’s difficult for traditional screws to create a strong grip. Sheet metal screws solve this problem by using sharp threads to create a strong grip.
Ease of Installation
Sharp threads also make sheet metal screws easy to install. The thicker or wider the threads, the more force a screw requires to install. Sheet metal screws have narrow and sharp threads, which makes them easier to install.
The sharp threads of sheet metal screws concentrate the pressure into a smaller area. Therefore, they penetrate into sheet metal and other materials more easily than other threads with wider threads.
Resistant to Pull-Out
Finally, sheet metal screws have sharp threads to increase their resistance to pull-out. Screws are often exposed to forces that try to pull them out. Pull-out resistance is a measurement of a screw’s ability to resist these external forces.
Sharp threads create a larger contract area between sheet metal screws and the object in which they are drive. The end result is improved resistance to pull-out.
