How to make parametrable parts in Solidworks 2010 ?
How could you make an assembly with the same part but with different sizes. For example using the same shaft part file for a 300mm and a 400mm shafts. The parts doesn't consist of simple extrusions as shafts but could have holes and complex shapes. I think about something cyclic as designing a shaft of 1mm and multiplying it in the assembly, or a pattern of 50mm long and making it a multiple of 50mm in the assembly. If possible making parts with flexible dimensions in different zones of the part (middle, between grooves ... etc).
There are many possibilities here, you can have equations relations at sketch part level. Then also have multiple configuration (design tables) at the part level such different lengths and diameters, etc. At the assembly level you can have multiple configurations of parts and/or suppress or unsuppressed parts depending on your requirements. These powerful tools that SW offers and if you know how to use them.