Nut Factor (K Factor)
Definition
A dimensionless coefficient relating applied torque to achieved bolt preload in the equation T = K × D × F. It accounts for friction in threads and under the bolt head or nut bearing surface.
Practical Note
K typically ranges from 0.10 (well-lubricated) to 0.20 (dry). Using incorrect K values can result in 50% or more error in achieved preload.