Small or medium-sized castings are made in flask— a box shaped container without top and bottom, which confines the sand moulds (Refer Fig. 3.28).
It is made in two parts, held in alignment by dowel pins. The top part is called the cope and the lower part is called the drag. If the flask is made in three parts, the centre one is called cheek. Metal flasks of steel or cast iron are usually used in production work because of their rigidity and permanence.
A snap flask is a small flask with a hinge on one corner and a snap catch on the other. With its use, moulds can be made repeatedly using the same flask.
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A moulding board and a bottom board complete the flask. The moulding board is a smooth board on which the flask and patterns are placed, when the moulding is started. When the mould is turned over, the function of this board is over. The mould is placed on a similar board called bottom board, which acts as a support for the mould until metal is poured in the mould.
Before any metal is poured into a mould, it is necessary that the flask be clamped in some way to prevent the buoyant effect of the molten metal from lifting up the cope. Small moulds are usually held down by flat cast iron weights, placed on the top of the moulds.
Larger flasks are usually held together by clamps, placed on the side or end either U- shaped clamps, held tight by driving wooden wedges under the end, or clamps that can be quickly adjusted to fit the height of the flask.
A gagger is a small L-shaped metallic accessory used in floor moulds to help support hanging bodies of sand in core. It is used only in large moulds having cross bars. The gagger is first coated with a clay wash and then placed next to one of the cross bars. The lower end should be close to the pattern, and the upper end should extend to the top of mould.
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The various other tools used are:
i. Showel:
It is used for mixing and tempering moulding sand and for moving the sand from pile to flask.
ii. Riddle or Sieve or Screen:
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It is used to remove bits of metal and foreign particles from the moulding sand. The size of the opening in the mesh indicates the size of the riddle.
iii. Rammers:
These are used to pack the sand evenly in the mould and for ramming into corners. The hand rammer is made of wood and resembles a handle less mallet with one end flat and the other a blunt wedge.
iv. Trowels:
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These are used to shape and smoothen the surface of the mould and for doing minor repairs. These are made of steel and are relatively long and narrow. The end of a trowel may be pointed, rounded or blunt.
v. Slicks:
These are spoon shaped trowels used for repairing or slicking (smoothing) a mould surface. They may be leaf shaped but are generally pointed.
vi. Lifters:
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These are long, narrow tools with hooked ends used for finishing work in tight places, doing repair work, or removing loose sand, which has fallen to the bottom of the mould.
vii. Draw Spikes:
These are used to remove the pattern from the mould and also for rapping the pattern gently to loosen it, from the sand to assure a clean draw.
viii. Swab:
It is made of flax or hemp and is used for applying water to the mould around the edge of the pattern. This prevents the sand edges from crumbling, when the pattern is removed from the mould.
ix. Rawhide Mallet:
It is used to loosen the pattern in the mould so that it can be with- drawn without damage to the mould. A rawhide mallet will not mar or deface the pattern as a metal mallet would.
x. Gate Cutter:
It is a piece of sheet metal used to cut the opening that connects the sprue with the mould cavity. This opening is called ‘gate’.
xi. Clamps:
These are used to hold the cope and drag of the completed mould together so that the scope may not float or rise, when the metal is poured into the mould.