In our projects we always get the 3D model of the screw from the manufacturer, 3D model repository, or design it in a CAD software. This is less work than developing an algorithm that can generate an entire screw at any size (and screws come in specific sizes anyway).
If you want to generate arbitrary screw sizes at runtime using VTK then you may be able to do it by applying scaling transform to a screw of similar size and/or cutting and assembling the screw from pieces.
If you really want to develop a screw generator algorithm then you can have a look at OpenSCAD scripts.