The ease with which a cast iron bar can be sprung is many times
overlooked. There is another peculiarity about cast iron, and likely
other metals, which an exaggerated example renders more apparent than
can be done by direct statement. Cast iron, when subject to a bending
strain, acts like a stiff spring, but when subject to compression it
dents like a plastic substance. What I mean is this: If some plastic
substance, say a thick coating of mud in the street, be leveled off
true, and a board be laid upon it, it will fit, but if two heavy
weights be placed on the ends, the center will be thrown up in the air
far away from the mud; so, too, will the same thing occur if a
perfectly straight bar of cast iron be placed on a perfectly straight
planer bed--the two will fit; but when the ends of the bar are bolted
down, the center of the bar will be up to a surprising degree. And so
with sliding surfaces when working on oil. If to any extent elastic,
they will, when unequally loaded, settle through the oil where the
load exists and spring away where it is not.

The tool post or tool holder that permits of a tool being raised or
lowered and turned around after the tool is set, without any sacrifice
of absolute stability, will be better than one in which either one of
these features is sacrificed. Handiness becomes the more desirable as
the machines are smaller, but handiness is not to be despised even in
a large machine, except where solidity is sacrificed to obtain it.

The weak point in nearly all (and so nearly all that I feel pretty
safe in saying all) small planing machines is their absolute weakness
as regards their ability to resist torsional strain in the bed, and
both torsional and bending strain in the table. Is it an uncommon
thing to see the ways of a planer that has run any length of time cut?
In fact, is it not a pretty difficult thing to find one that is not