<P> Today machine tools are typically powered other than by human muscle (e.g., electrically, hydraulically, or via line shaft), used to make manufactured parts (components) in various ways that include cutting or certain other kinds of deformation . </P> <P> With their inherent precision, machine tools enabled the economical production of interchangeable parts . </P> <P> Many historians of technology consider that true machine tools were born when the toolpath first became guided by the machine itself in some way, at least to some extent, so that direct, freehand human guidance of the toolpath (with hands, feet, or mouth) was no longer the only guidance used in the cutting or forming process . In this view of the definition, the term, arising at a time when all tools up till then had been hand tools, simply provided a label for "tools that were machines instead of hand tools". Early lathes, those prior to the late medieval period, and modern woodworking lathes and potter's wheels may or may not fall under this definition, depending on how one views the headstock spindle itself; but the earliest historical records of a lathe with direct mechanical control of the cutting tool's path are of a screw - cutting lathe dating to about 1483 . This lathe "produced screw threads out of wood and employed a true compound slide rest". </P> <P> The mechanical toolpath guidance grew out of various root concepts: </P>

What is the basic function of tool holders