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CUTTING INSTRUMENTS. 35

class of instruments should have careful study. The hatchet
ordinaries should be ground to a thin edge equally beveled on
the two sides — bibeveled — and the degree of bevel should be
the same at each grinding. The motion in grinding should be the
full length of the stone at each strol^e, and a finger rest on the
face of the stone, or of its box, should slide with the stroke in
order to maintain the particular angle of the blade to the stone
throughout the length of each stroke in order that the grinding
will be flat. One principal fault observed in the sharpening of
hatchet ordinaries is the tendency to rounding of the edges
instead of keeping them straight, square with the blade, and the
angles with the blades sharp and definite. These instruments
do the best work when their edges are ground in this form. This
is true of all dental cutting instruments except the gingival
margin trimmers, which are made with a special angle of cutting
edge, which adapts it to one special purpose.
The hoes have only one bevel. This is on the distal side of
the blade. They are ground on that side only. These are used
mostly with a scraping motion, and for this purjiose a short bevel
is best. A bevel of ten to twelve centigrades is good. In grind-
ing the hoes, the blades of which are twelve centigrades angle
with the shaft, the shaft will stand almost perpendicular to the
surface of the stone in order to obtain this bevel. If the edge
is turned from the operator, the grinding should be done mostly
with the pull motion. On the push movement, the instrument is
likely to chatter if pressure is used. The hoes with twenty-three
centigrades angle of blade should be placed on the stone with
the edge down and the shaft inclined toward the operator suffi-
ciently to give the correct bevel of the blade, and in the move-
ment back and forth the principal pressure should be applied on
the push motion. It is not difficult, with a little careful attention,
to keep the edge straight and square with the blade. The hoes
of six centigrades angle must also have their particular position
on the stone to give their blades the proper bevel. With the end
of the stone to the hand, lay the beveled side of the hoe down-
ward with the point toward the distant end of the stone. Then
raise the handle until the blade is at the proper angle with the
surface of the stone to give the correct bevel in grinding. Then
use that particular position in grinding all of the hoes of this
angle. From this it will be seen that each class of point has its
particular position on the stone for each of its angles. The size
of the blade does not affect its relation to the stone. For each
instrument we use, the best relation to the stone for that form