Manually controlled metalworking lathes are commonly provided with a variable-ratio gear-train to drive the main lead-screw. This enables different thread pitches to be cut. On some older lathes or more affordable new lathes, the gear trains are changed by swapping gears with various numbers of teeth onto or off of the shafts, while more modern or expensive manually controlled lathes have a quick-change box to provide commonly used ratios by the operation of a lever.