Allowances for pattern : A pattern is always made larger than the required size of the casting in order to allow for various factor, such as shrinkage, machining, distortion and rapping etc. The following allowances are provide in a pattern :
1. Shrinkage allowance
2. Draft allowance
3. Machining allowance
4. Rapping or shake allowance
5. Mould wall movement allowance
6. Distortion allowance