_SLOTTING MACHINES._
Slotting machines with vertical cutting movement differ from
planing machines in several respects, to which attention may be
directed. In slotting, the tools are in most cases held rigidly and
do not swing from a pivot as in planing machines. The tools are
held rigidly for two reasons; because the force of gravity cannot
be employed to hold them in position at starting, and because the
thrust or strain of cutting falls parallel, and not transverse to
the tools as in planing. Another difference between slotting and
planing is that the cutting movement is performed by the tools
and not by movement of the material. The cutting strains are also
different, falling at right angles to the face of the table, in the
same direction as the force of gravity, and not parallel to the
face of the table, as in planing and shaping machines.
The feed motion in slotting machines, because of the tools being
held rigidly, has to operate differently from that of planing
machines. The cross-feed of a planing machine may act during the
return stroke, but in slotting machines, the feed movement should
take place at the end of the up-stroke, or after the tools are
clear of the material; so much of the stroke as is made during the
feeding action is therefore lost; and because of this, mechanism
for operating the feed usually has a quick abrupt action so as to
save useless movement of the cutter bar.
The relation between the feeding and cutting motion of
reciprocating machines is not generally considered, and forms an
interesting problem for investigation.
(1.) Name some of the differences between planing and slotting
machines.--(2.) Why should the feed motion of a slotting machine
act abruptly?--(3.) To what class of work are slotting machines
especially adapted?