Across Flats (A/F)
Definition
The distance between two parallel flat surfaces of a hex bolt head or nut, measured perpendicular to the axis. This dimension determines the wrench size needed to tighten the fastener.
Practical Note
SAE and metric fasteners of similar size may have different across-flats dimensions. Always use the correct wrench size to avoid rounding the hex corners.
Related Calculators
🔧Bolt Size Chart
Interactive bolt size reference. Look up head dimensions, thread specifications, recommended hole sizes, and matching nut dimensions for hex bolts in SAE and metric standards.
🔧Bolt Torque Calculator
Calculate bolt torque, preload force, and clamping force for threaded fasteners. Supports metric and imperial threads.