Figure 12.—Well-developed example of lathe headstock having several leads on the spindle and provision for mounting the work or a work-holding chuck on the spindle. Adapted from L’Encyclopédie, vol. 10, plate 13.
Figure 13.—End view of the headstock seen in [figure 12], showing the keys or half nuts which engage the threaded spindle, in engaged and disengaged positions. From L’Encyclopédie, vol. 10, plate 13.
Figure 14.—Spindle of figures [12] and [13], showing the several leads and the many-sided seat for the driving pulley. Note the scale of feet. From L’Encyclopédie, vol. 10, plate 16.
Roughly twenty years later, Joseph Nason of New York patented [4] the commercially very important “Fox” brassworker’s lathe ([fig. 18]). While this does have a ratio in the pair of gears connecting the work spindle and master screw, it is clear from the patent that various pitches are to be obtained by changing screws, not by changing gears. The patent sums it up as follows: