Page 57 - My FlipBook

CUTTING INSTRUMENTS. 21

MoN-ANGLE. An instrument having one angle only leading
to the working point, as in pluggers, or in the blades of exca-
vators. Mon-angles form a large majority of ordinary hatchet
and hoe excavators. In the more considerable angles only the
shorter blades can be successfully used as mon-angles, for the
reason that when the blade is long, its inclination carries its
working point laterally so far from the central line of the shaft
as to render the instrument liable to turn in the hand when the
edge is forcibly applied, as the instruments in Figure 15. This
renders the instrument unsteady and ineffective.
CoNTRA-ANGLE. All cuttiug instruments, in which the angle
and length of blades will carry the cutting edges more than
three millimeters from the line of the central axis of the shaft,
should be contra-angled, as in Figure 16. In the contra-angles
there are the binangles and the triple-angles.
BiNANGLE coNTRA-ANGLE. In au instrument of the angle of
12 centigrades or less, the binangle contra-angle will bring
the cutting edge sufficiently near the central line of the shaft,
and at the same time carry the shank sufficiently out of the way
to permit the use of the full length of the blade (see enamel
hatchets and spoons. Figure 22). In forming a binangle contra-
angle the shank of the instrument is first bent backward (from
the direction of the cutting edge), and nearer the cutting edge
another bend is made forward — this length forming the blade,
the object being to form a long blade, the edge of which will be
near the central line of the shaft, as shown in Figure 16.
Triple-angle contra-angle. In instruments of a greater
angle than 12 centigrades a binangle will not bring the cutting
edge sufficiently near the central line of the shaft, therefore a
triple-angle contra-angle must be made (see hatchet 12-5-23 and
hoe 12-5-23, Figure 22). This is done by first bending the shank
backward, as in the binangle contra-angle, and then forming
another angle which will bring the remainder of the shank par-
allel with the shaft; then passing forward a space of more or
less length as may be required, another bend is made forward by
which the blade is formed. In this way the cutting edge of a long
blade is brought sufficiently near the central line of the shaft for
effective work and the shank carried sufficiently out of the way
to permit the full use of the length of the blade.
Long blades that require contra-angling are mostly for use
in places where a long reach of blade is necessary. (See long
hatchets and long hoes, Figure 21.)