Drills and lathes have been used since ancient times, albeit in crude and primitive forms. During and after the Middle Ages, several other machine tools were created that played an important role in the Industrial Revolution. The lathe is undoubtedly the most important machine tool. The ornamental lathe was one of the first machine tools to undergo major improvements. In the eighteenth century, it achieved great success by being able to create complex arabesques and other figures using cams. Turret lathes appeared in the mid-nineteenth century. By mounting multiple tools on the turret, different machining operations could be performed without stopping the lathe to change tools. In 1870, C. M. Spencer converted a manual turret lathe into an automatic cam-type lathe. Since that time, cam-type automatic lathes have been widely used because of the advantages they offer in high-volume production. Later, cams were used to operate many of the automatic devices that were introduced on lathes. This led to a further increase in production speed and a reduction in direct operator intervention. Automatic cam-type lathes became widespread and dominated the industry until the advent of numerical control. In addition to lathes, cams have been used to automate several other machine tools. These are mentioned only briefly in this book.