screw

A screw is a type of mechanical fastener predominantly used to join materials together, typically made of metal, plastic, or other durable materials. It consists of a cylindrical shaft with a helical ridge, known as a thread, wrapped around its surface. The threads enable the screw to be driven into a material, creating a secure joint through rotational force.

Screws are distinguished from bolts by their intended use and design features. While bolts usually require nuts to fasten components, screws often cut into the material itself, providing anchorage through their threads. They are commonly used in woodworking, metalworking, and plastic assembly applications.

The head of a screw varies in shape according to the type of drive required to turn it—examples include flat (slotted), Phillips, Torx, and hex heads. The choice of head type influences the torque applied and ease of installation or removal.

Screws can be classified based on their application, thread type, and design. For example, wood screws generally have coarse threads suitable for soft materials, while machine screws feature finely machined threads for use with tapped holes or nuts. Self-tapping screws are designed to create their own internal threads when driven into pre-drilled or soft materials.

The manufacturing of screws involves processes like cold forming or machining, ensuring precise dimensions and strong thread formations. Proper selection of screw type and material is crucial for ensuring the structural integrity and longevity of the joint, especially in environments exposed to moisture, stress, or temperature variations.

Overall, screws are versatile fasteners integral to countless construction, manufacturing, and repair tasks, valued for their simplicity, strength, and reliability.