To do away with the inconvenience and loss of time involved in removing and replacing change gears

To do away with the inconvenience and loss of time involved in removing and replacing change gears, most modern lathes have a self- contained change gear mechanism, commonly called a “quick-change gear box.” There are a number of types used on different types of lathes, but they are all similar in principle The quick-change gearbox mechanism consists of a cone-shaped group of change gears. One can instantly connect any single gear in the gear train by a sliding tumbler gear controlled by a lever. The cone of gears is keyed to a shaft which drives the lead screw (or feed rod) directly or through an intermediate shaft. Each gear in the cluster has a different number of teeth and hence produces a different ratio when connected in the train