Screw threads, fasteners and locking devices

Screw threads are spiral grooves cut on cylindrical surfaces that allow two parts to connect and tighten together. Think of them like the threads on a bottle cap—when you turn it, the grooves grip and hold everything secure. In technical drawing, we represent threads using simple conventional symbols rather than drawing every single groove, which would waste time and look messy.

Fasteners are devices like bolts, nuts, and screws that hold things together permanently or temporarily. You see these daily in Nigerian construction sites holding steel beams together, or in vehicles securing engine components. Locking devices like washers and lock nuts prevent fasteners from loosening due to vibration or movement.

To draw threads conventionally, we use thin parallel lines at an angle along the shaft. For nuts and bolts, simple hexagonal shapes represent their tops. Understanding these symbols helps you read engineering drawings correctly.