Pattern differs from a finished casting

 

MOULDING PATTERN

A model of anything  so constructed that it may be used for forming a mould or impression in damp sand or other suitable material is known as a pattern .The mould produced with the help of a pattern ,when filled with molten metal or substances that solidify ,forms a reproduction of the pattern and is known as a casting .pattern differs in a number of respects from the resulting casting these differences known a pattern allowances ,compensate for metal shrinkage ,provide sufficient metal for machined surface ,and facilitate moulding .A through understanding of these allowances is necessary for successful pattern design and construction .