Figure 5-27.--Checking the squareness of the end of a
Figure 5-29.--Sharpening a cold chisel.
To sharpen this chisel, hold it to the wheel, resting
screwdriver. Views B and D are the side views.
Dress the edges so the blade is symmetrical in shape,
the index finger, curved beneath the chisel, rides
then square off the end. Check the squareness of the
against the front edge of the tool rest. This ensures
end by using a square. If the blade and shank appear
control of the chisel and will help you grind a single,
equal bevel on each side.
Next, grind the faces of the blade so they are
Let the chisel rest lightly against the wheel while
parallel at the tip as shown in views B and D of figure
grinding. This will develop less heat and the air
5-26. The thickness of the blade at the tip should be
currents created by the wheel will have the maximum
such that the tip will just enter the slot of the screw
cooling effect. Be sure the cutting edge is kept cool or
you intend to turn. With such a tip thickness, and the
sides parallel, the screwdriver will have the least
tendency to climb out of the screw slot when the
screw is being turned. When grinding, do not let the
tip get too hot or it will be softened.
Metal-cutting chisels: These chisels are
designed to cut cold metal, so we often use the general
term cold chisel to describe them. The 60° angle
Increase this angle to cut harder materials and
Figure 5-30.--Specifications for grinding a regular point twist
decrease it for softer materials.
Figure 5-31.--Specifications for grinding a flat point twist
Figure 5-28.--Proper angle for a general use cold chisel.