Blading and Tempering Dental Excavators. [Volume: 2, Issue: 8, March, 1861, pp. 419-421]

420

THE DENTAL COSMOS.

Great care should now be exercised not to turn the blade while the temperature is much reduced. If the blade has cooled before the desired
angle is obtained, place it in the flame, and when heated to the right
temperature the desired angle may be obtained by turning the blade while
in the flame by successive strokes of the hammer, or with the pliers, or
it may be turned as at first on the anvil. The blade may now be hammered to an edge, and the cutting edge put on with the file and stone.
Hoes.-The preparation of this class of excavators is the same as the
two other classes, but requires the use of the file more than the others to
produce the several cutting edges which this class of excavators requires.
As this class of excavators has nearly all their blades at right angles, care
should be taken in turning to have them at the cherry-red temperature.
All blades should have sharp angles and not curved ones. After the
blade is turned, it is then hammered to the required thickness and the
edges made with the file.
Polishing. —If the hammer and anvil have perfectly smooth faces they
will also leave the instrument correspondingly smooth, and facilitate much
this part of the operation of instrument making. The most efficient way
to polish excavators is to use first fine emery upon a buff wheel on the
lathe, a little sweet oil being used with the emery, then burnish with a
blood-stone or steel burnisher. After this another buff wheel is used with
rouge (calcined sulphate of iron) and alcohol. The buff wheels should
be covered upon their peripheral surface with soft leather. When this is
gone through, the instrument is ready for
Tempering.-The first thing to be done in tempering is the hardening
of the steel, which may be done in the following way. Having provided
ourselves with some substance with which to coat the steel to keep it from
oxidizing on the surface, Castile soap is very good, we will proceed
by putting a slight coating of the soap (or any substance that will
prevent oxidization) over the part of the instrument to be hardened,
heat to a bright cherry-red temperature, and plunge instantly into cold
water, which should be very near to the flame, so that the temperature
may not be reduced before it is suddenly cooled in the liquid. Equal
parts of water and muriatic acid may be used as a cooling liquid with
very good results, making the steel tenacious. If it has been sufficiently
hardened by this process, the coating will have left the instrument quite
clean and of a silvery appearance, and will also resist the action of a file.
The instrument is now too hard for use, and will have to be drawn to the
required temper. Polish again upon the buff wheel with rouge before
you proceed to draw the temper, that the temper colors may be distinctly
seen. Care should be taken not to break them while polishing, as they
are very brittle. Having ready the cooling liquid and a small spiritlamp, place the shaft of the instrument of which the temper is to be
drawn in the flame of the spirit-lamp, about one inch and a half from the