(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Modern Mechanical Engineering Vol-I"

96

PATTERN-MAKING

7. PLATED  PATTERNS

The practice of attaching patterns to plates has grown enormously in
consequence of the immense developments of machine-moulding. But it
ante-dated this, and is in extensive use apart from the aids afforded by
machines. It is derived from and is an extension of the employment of
joint or bottom boards.

Bottom Boards.—The bottom or joint boards, which are stocked in

many sizes in foundries,
are made of thick, narrow
strips with open joints
united with battens. They
have holes bored to receive
the pins of the bottom
parts of moulding-boxes,
and are of general utility,
since any patterns that
will go in a box can be
rammed on the bottom
board. Two results are
achieved, one being that
the ramming of a dummy
mould, for the sole pur-
pose of getting a joint
face, is avoided; the other
that the board affords a
level bed for the pattern,
so avoiding risk of its
winding during ramming.
Permanent Plates.
—At an early stage, when
work becomes repetitive,
an obvious economy is
secured by attaching pat-
terns to boards, and
making these and the

fitted boxes a permanent working unit. But then only the bottom box
can be rammed on the board; the cope must still be rammed on the joint
face of the bottom box, turned over to receive it. The next stage there-
fore is to attach the two portions of a pattern to a single board (fig. 77),
without battens, and to fasten both box parts together with the pins passing
through holes in the board. Here, though turning over is necessary, the
advantage remains that both joint faces are provided by the board, and that
both halves of the pattern are prevented from bending or winding. A more
advanced stage is that in which each half or portion of a pattern is attached

- 77.—Wooden Cock Pattern mounted on a Joint Board