A quantity of sand sufficient to
completely cover the pattern is then sifted into the drag, which
is then filled level with the top with unscreened sand. This is
rammed down slightly with the rammer, and then more sand is added
until
[Illustration: Fig,. 3-Making a Mold]
it becomes heaped up as shown at B. It is then rammed again as
before.
It is impossible to describe just how hard a mold should be
rammed, but by observing the results the beginner can tell when a
mold is too hard or too soft, and thus judge for himself. If the
sand falls out of the flask when lifting the cope, or if it opens
up or spreads after it is poured, it shows that the mold has been
rammed too little, and if the surface of the sand next to the
pattern is cracked it shows that the mold has been rammed too
hard. It will be found that the edges of the mold can stand a
little more ramming than the middle. In finishing the ramming,
pound evenly all over the surface with the blunt end of the
rammer.
After ramming, scrape off the surplus sand with a straight-edged
stick, as shown at C, and scatter about 1/16 in.
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