may well indicate that the tool
was made for use with a lead of coarser pitch, now lost.

[Illustration: Figure 4.--THE WORKING AREA of figure 3, showing the tool
and signature. (Smithsonian photo 46525A.)]

Perhaps the most startling feature of this machine when compared with
the machine of the _Hausbuch_, is the absence of a cross-slide for
adjusting the tool. Possibly this can be explained by the blunt scraping
edge on the tool. In actual use, recently, to cut a sample screw, using
a tool similar to the one found in the machine (fig. 7), it was found
advantageous to be free of a cross-slide and thus be able to feed the
tool into the work by feel rather than by rule, as would be done with a
slide rest. In this way, it was possible to thread steel without
tearing, as the cutting pressure could readily be felt and the tool
could release itself from too heavy a cut. Size on several screws could
be repeated by setting the tool to produce the desired diameter when its
supporting arm came to rest against the frame of the machine. The screws
used in the machine itself were apparently made in just such a way. They
were not cut with a die as the thread blends very gradually into the
body of the screw without the characteristic marks left by the cutting
edges of a die. Threads cut with a single-point tool controlled by a
cross-slide usually end even more abruptly than those cut by a die,
while it would be quite simple with a machine of the nature we are
considering to bring the thread to a gentle tapering end as seen in
figure 8 (another view of the screw A in fig. 3) by gradually releasing
the pressure necessary to keep the tool cutting as the end of the
thread was approached.

[Illustration: Figure 5.--SPRING FOR KEEPING THE FOLLOWER SPINDLE
against the work, showing the method and range of adjustment. Note the
rectangular projection to engage a mating socket in the spindle, to
prevent spindle rotation. (Smithsonian photo 46525.)]

[Illustration: Figure 6.--WORK SPINDLE AND ITS NUT removed from the
machine to illustrate how easily another spindle and nut of different
pitch could be substituted. (Smithsonian photo 46525C.)]

That machines of this general type having the lead screw on the axis of
the work were competitive with other methods and other types of machines
over a long period of time may be seen from figures 9 and 10. The
machine, left front in figure 9 and in more intimate detail in figure
10, can be seen to di