Slotted Drive (Flat Head)
Direct Answer
The Slotted drive (Flat Head / Flat Blade) is the original single-slot fastener drive geometry standardized under ISO 2380 and DIN 963. Operated with a flat screwdriver blade, it features no inherent centering or cam-out retention, making it susceptible to tool slippage and strictly limited to manual assembly and decorative restoration.
Source: ISO 2380 / DIN 963 / ASME B18.6.3
Specs
| Standard Specifications | ISO 2380 (Screwdrivers) / DIN 963 / ASME B18.6.3 |
| Drive Geometry | Single linear rectangular slot through head center |
| Self-Centering Capability | None (Driver freely slides laterally out of slot) |
| Cam-Out Tendency | Extremely High (Tends to climb up and out of slot under torque) |
| Power Tool Suitability | Unsuitable (High risk of workpiece scratching / bit slippage) |
| Primary Modern Applications | Antique furniture restoration, electrical switch wallplates, plumbing fixtures |
Historical Context and Mechanical Limitations
Dating back to the 15th century, the slotted screw was the easiest to manufacture using basic metal saws. However, because the driver blade lacks lateral containment, applying rotational torque naturally pushes the blade out of the slot (cam-out), scratching adjacent surfaces. When 20th-century automotive assembly lines automated screw insertion, slotted screws were quickly replaced by self-centering cruciform drives.
Modern Architectural Usage
Slotted screws remain ubiquitous on decorative North American light switch and electrical outlet cover plates (#6-32 oval head slotted screws), where electricians align all slot grooves vertically as an aesthetic trade convention.