A nut driver’s size is determined by the metric measurement across the flats of the hexagonal or square socket opening. These precise measurements ensure a snug fit with corresponding fasteners, preventing slippage and damage. For example, a 5 mm nut driver fits a 5 mm nut or bolt head.
Accurate sizing is critical for effective torque application and preventing rounded fasteners. The metric system offers a standardized, globally recognized system of measurement, facilitating international compatibility and simplifying tool selection. Historically, the transition to metric sizing provided a more logical and consistent approach compared to imperial fractional sizes.
