Having introduced the improved "Model D" Atlas 10-inch of 1936 that addressed many of the machine's earlier weaknesses ("D" was not a catalog description but cast into various parts and so a handy way of referring to the model) further changes were made with the Model F in 1937. With the arrival of WW2 nothing else was changed on the lathe until 1947 when the option was offered of the Models QC42 and QC54 fitted with quick-change screwcutting and feeds gearboxes. In addition the gearbox and its associated parts were offered as a conversion kit for earlier models - or to upgrade later lathes bought with changewheel screwcutting.