Yarn Spinning & Preparation
Actual draft comes from the material; mechanical draft comes from the gearing. The gap between them is slippage.
— x
Doublings x hank delivered / hank fed
Slippage above about 5% points to worn top rollers, wrong pressure or an over-long break draft. Recalculate the constant whenever the gearing train is changed.
Draft & Draft Constant Calculator — free, with the formula and a worked example, at Textile School.