FRANK A. TAYLOR _Director, United States National Museum_ CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY: PAPER 37 SCREW-THREAD CUTTING BY THE MASTER-SCREW METHOD SINCE 1480 _Edwin A. Battison_ _Edwin A. Battison_ SCREW-THREAD CUTTING BY THE MASTER-SCREW METHOD SINCE 1480 _Among the earliest known examples of screw-thread cutting machines are the screw-cutting lathe of 1483, known only in pictures and drawings, and an instrument of the traverse-spindle variety for threading metal, now in the Smithsonian Institution, dating from the late 17th or early 18th century. The author shows clearly their evolution from something quite specialized to the present-day tool. He has traced the patents for these instruments through the early 1930's and from this research we see the part played by such devices in the development of the machine-tool industry._ THE AUTHOR: _Edwin A. Battison is associate curator of mechanical and civil engineering in the Smithsonian Institution's Museum of History and Technology._ Directness and simplicity characterize pioneer machine tools because they were intended to accomplish some quite specialized task and the need for versatility was not apparent. History does not reveal the earliest forms of any primitive machines nor does it reveal much about the various early stages in evolution toward more complex types. At best we have discovered and dated certain developments as existing in particular areas. Whether these forms were new at the time they were first found or how widely dispersed such forms may have been is unknown. Surviving evidence is in the form of pictures or drawings, such as the little-known screw-cutting lathe of 1483 (fig. 1) shown in _Das mittelalterliche Hausbuch_. This lathe shows that its builder had a keen perception of the necessary elements, reduced to bare essentials, required to accomplish the object. Present are the coordinate slides often credited to Henry Maudslay. His slides are not, of course, associated with the spindle; neither is there any natural law which compels them to guide the tool exactly parallel with the axis of revolution. In this sense the screw-cutting lathe in the _Hausbuch_ is superior because it is in harmony with natural law and can generate a true cylinder, whereas Maudslay's lathe can only transfer to the work whatever accuracy is built into it.