Learn to use modeling techniques that allow for efficient transition between part design and delivery of the finished castings. Create a motorcycle gear case by designing the production tooling for the part. Start by designing the core, or the negative space, of the gear case. Design the pattern, or outside faces, of the gear case as a separate solid body. Save the tooling bodies as new part files. Combine the solid bodies, subtracting the core from the pattern. Apply machining features to finish the model.