Official Answer
Answer
To achieve a target preload $P_t$, the cavity depth $H_c$ must be precisely calculated based on the spring's free height $H_f$ and its rate $k$. The formula is $H_c = H_f - (P_t / k)$. However, the engineer must account for the tolerance stack-up of the housing, the mating component, and the spring itself. Using the Root Sum Square (RSS) method for tolerances: $T_{assembly} = \sqrt{T_{spring}^2 + T_{housing}^2 + T_{component}^2}$. If the target preload has a tight tolerance (e.g., $± 5$ lbs), it may be necessary to use shims or to measure and 'bin' the springs by their actual rate to ensure the final assembly falls within the required performance window.
