possible--nothing short of casting the apron in the same piece will be
strong enough, because with a long, elastic guide heavy work will
spring it down and wear it away at the center, and then with light
work it will ride at the ends, with a chattering cut as a consequence.

An almost endless and likely profitless discussion has been indulged
in as to the proper way to guide a slide rest, and different opinions
exist. It is a question that, so far as principle is concerned, there
ought to be some way to settle which should not only govern the
question in regard to the slide rest of a lathe, but all slides that
work against a torsional resistance, as it may be called--that is, a
resistance that does not directly oppose the propelling power. In
other words, in a lathe the cutting point of the tool is not in line
with the lead screw or rack, and a twisting strain has to be resisted
by the slides, whereas in an upright drill the sliding sleeve is
directly over and in line with the drill, and subject to no side
strain.

Does not the foregoing statement that "the propelling power should be
as near the resistance as possible, and the guide be as near in line
with the two as possible," embody the true principle? Neither of the
two methods in common use meets this requirement to its fullest
extent. The two-V New England plan seems like sending two men to do
what one can do much better alone; and the inconsistency of guiding by
the back edge of a flat bed is prominently shown by considering what
the result would be if carried to an extreme. If a slide such as is
used on a twenty inch lathe were placed upon a bed or shears twenty
feet wide, it would work badly, and that which is bad when carried to
an extreme cannot well be less than half bad when carried half way.