Draft allowance-

A taper of 0.01 to 0.025mm/mm is generally provided on the vertical faces of the patterns for its easy withdrawl from the mould. The taper is called the draft allowance.

Shrinkage allowance-

Shrinkage allowance is provided to compensate for contraction of the casting when the temperature of the solidifying metal in the mould cavity drops from freezing to room temperature. Shrinkage allowance is generally in the range of 0.01 to 0.016mm/mm, depending upon the type of material.

Pattern and mould-

A pattern is a replica of the desired casting and is used for making the mould cavity. Various types of patterns are used in casting - the choice depending upon the production quality and the casting configuration. Single-piece patterns are obviously least expensive but have limited applications. Split patterns or two piece patterns are most widely used since it can be easily withdrawn from the mould and can be used for intricate shapes.
Patterns are always made somewhat larger than the final casing to allow for shrinkage, distortion and finishing. These are taken care by shrinkage, draft, finish, distortion and shake allowances.

Pattern and mould-

A pattern is a replica of the desired casting and is used for making the mould cavity. Various types of patterns are used in casting - the choice depending upon the production quality and the casting configuration. Single-piece patterns are obviously least expensive but have limited applications. Split patterns or two piece patterns are most widely used since it can be easily withdrawn from the mould and can be used for intricate shapes.
Patterns are always made somewhat larger than the final casing to allow for shrinkage, distortion and finishing. These are taken care by shrinkage, draft, finish, distortion and shake allowances.