Which type of screw is primarily used for joining two pieces of sheet metal?

The type of screw primarily used for joining two pieces of sheet metal is the sheet metal screw. This screw is specifically designed with sharp threads that can easily penetrate metal surfaces without needing a pre-drilled hole, which makes it ideal for metal applications. The threads provide a strong grip and prevent the screw from loosening under vibration or movement, which is a common concern in metalworking.

Sheet metal screws often feature a pointed tip that helps in starting the screw into the metal, ensuring a secure connection between the two sheets. Additionally, they are made from materials that resist corrosion, contributing to the durability of the assembly.

Other types of screws, such as wood screws or metal screws, are not optimized for the unique properties of sheet metal. Self-tapping screws, while often used in metal applications, are generally a broader category that can include sheet metal screws, but sheet metal screws are specifically tailored for that purpose, making them the preferred choice for this specific task.