I want to know the purpose of parting line Solution A parting line is the border in which draft angles change direction. It is also the line, which splits the part into core and cavity halves. Parting line can be a starting point for the mould parting surface, but not necessarily. In other words we can say that Parting line in actual seperates Cope and Drag of a mould and hence plays an important role in determining various properties, shapes and surface finish of Cast..