most primitive as well as the simplest of all tools for the
dividing of wood into parts, is the wedge. The wedge does not
even cut the wood, but only crushes enough of it with its edge
to allow its main body to split the wood apart.
As soon as the split has begun, the
edge of the wedge serves no further purpose, but the sides bear
against the split surfaces of the wood. The split runs ahead of
the wedge as it is driven along until the piece is divided.
It was by means of the wedge that
primitive people obtained slabs of wood, and the great change
from primitive to civilized methods in manipulating wood
consists in the substitution of cutting for splitting, of edge
tools for the wedge.
The wedge follows the grain of the
wood, but the edge tool can follow a line determined by the
worker. The edge is a refinement and improvement upon the wedge
and enables the worker to be somewhat independent of the natural
grain of the wood.
In general, it may be said that the
function of all cutting tools is to separate one portion of
material from another along a definite path.
All such tools act, first, by the
keen edge dividing the material into two parts; second, by the
wedge or the blade forcing these two portions apart. If a true
continuous cut is to be made, both of these actions must occur
The edge must be sharp enough to
enter between the small particles of material, cutting without
bruising them, and the blade of the tool must constantly force
apart the two portions in order that the cutting action of the
edge may continue.
The action of an ax in splitting wood is not a true cut, for
only the second process is taking place, Fig. 59. The split
which opens in front of the cutting edge anticipates its cutting
and therefore the surfaces of the opening are rough and torn.
When a knife or chisel is pressed into a piece of wood at right
angles to the
grain, and at some distance from the end of the wood, a continuous cutting action is prevented, because soon the
blade cannot force apart the sides of the cut made by the
advancing edge, and the knife is brought to rest.
In this case,
it is practically only the first action which has taken place.