In practice there is occasionally found a slight irregularity in the
thickness of slugs, and thin fins are sometimes cast around the forward
edges. For the purpose of reducing them to a uniform thickness, they are
driven on their way to the galley between two vertical knives, as shown
in Figs. 4 and 16. The inner knife is stationary, but the outer knife is
adjustable in order that it may accommodate slugs of different
thicknesses. This adjustment is made by the knife being seated at its
outer edge against a supporting bar or wedge, having at opposite ends
two inclined surfaces seated against supporting screws in the
knife-block. A lever engages a pin on the wedge for the purpose of
moving it endwise; when moving in one direction, it forces the knife
inward toward the stationary knife, and when moved in the other
direction, it forces it to retreat under the influence of a spring
seated in the block. The wedge is provided with a series of teeth
engaged by a spring-actuated pin or dog, whereby the wedge and the knife
are stopped in proper positions to insure the exact space required
between the two knives.
[Illustration: Fig. 15.]
The back knife, secured to the frame for trimming the base of the slug
as it is carried past by the revolving wheel, should be kept moderately
sharp and adjusted so as to fit closely against the back of the passing
mold. Particular attention should be paid to this feature. The edge of
the knife must bear uniformly across the face of the mold.
[Illustration: Fig. 16.]
The front knives, between which the slug is ejected, should not be made
too sharp. After being sharpened, the thin edge can be advantageously
removed by the use of a thin oilstone applied against the side face;
that is, against the face past which the slug is carried.
The stationary or left-hand knife should be so adjusted as to align
exactly with the inner side of the mold. Under proper conditions this
knife does not trim the side face of the slug, but acts only to remove
any slight fins or projections at the front edge.
The right-hand knife, adjustable by means of a wedge and lever, should
stand exactly parallel with the stationary knife. It trims the side of
the slug on which the ribs are formed, and it serves to bring the slug
to the exact thickness required.