When electric motors started to become common in the early 20th century, many cone-head lathes were converted to electric power. At the same time the state of the art in gear and bearing practice was advancing to the point that manufacturers began to make fully geared headstocks, using gearboxes analogous to automobile transmissions to obtain various spindle speeds and feed rates while transmitting the higher amounts of power needed to take full advantage of high speed steel tools. Cutting tools evolved once again, with the introduction of man made carbides, and became widely introduced to general industry in the 1970s. Early carbides were attached to toolholders by brazing them into a machined 'nest' in the tool holders. Later designs allowed tips to be replaceable and multi faceted, allowing them to be reused. Carbides tolerate much higher machining speeds without wearing. This has led to machining times shortening, and therefore production growing. The demand for faster and more powerful lathes controlled the direction of lathe development.