OF DRAWING PATTERN SPIKE AND
RAPPER.]

At the risk of appearing pedantic, but with a view to developing an
appreciation of the true function of the method of pattern drawing
used in this machine, attention is called to the following sectional
views of moulds and ways of drawing patterns occurring in machine
moulding. Fig. 1 shows an ordinary "gate" of fitting patterns being
drawn from the drag or nowel part of the mould by means of a spike and
rapper wielded by the moulder's hand after cope and drag have been
rammed together on a "squeezer" and cope has been removed. Frequently
the pernicious "swab" is used to soak and so strengthen joint outlines
of the sand before drawing patterns, in such cases as this. In this
case, before cope is lifted, these patterns must be vigorously rapped
through the cope; an amount depending (and so does the size of the
casting) upon the mood and strength of the moulder.

Fig. 2 shows the stripping or drop plate method of drawing patterns.

[Illustration: FIG. 2.--STRIPPING PLATE METHOD OF DRAWING PATTERNS.]

In this method the patterns are not rapped at all and are drawn in a
practically straight line so that the mould is absolutely pattern
size.

The stripping plate is fitted accurately to every outline at the joint
surface of the patterns, obviously at considerable expense, and, of
course, at the instant of drawing the patterns, supports the joint
surface of the mould entirely. This is, at first sight, an ideal
method of drawing patterns, and it has for years been the only method
practiced on machines. It has two disadvantages. The patterns are
separated from the stripping plate by the necessary joint fissure
between the two. Fine sand continually falls into this and, adhering
to the joint surfaces more or less, grinds the fissure wider. This
leads to a gradual reduction of size of patterns on vertical surfaces
and a widening of the joint fissure often to such an extent that wire
edges are formed on the mould, causing, on fine work, "crushing" and
consequently dirty joints. A nicely fitted but worn plate of
twenty-four pieces which had cost, at shop expense only, $250, was
recently replaced by a plate of twenty-eight pieces, fitted ready for
the machine under the new system about to be described, for not more
than $25.

The stripping plate method has another drawback, not always
appreciated, probably because accepted as inevitable. Stripping plate
patterns are not rapped, and ther