http://www.alibre.com/
https://www.alibre.com/xpress/software/alibre-design-xpress.asp
Alibre Design Xpress 3D Solid Modeler
Ready to get started with a real parametric solid modeler, but don't want to spend a bundle? Alibre Design Xpress is a rich and capable 3D solid modeler for creating mechanical parts, assemblies and 2D drawings - and is free. Certain more elegant features, like 3D sketching and part Booleans, can be found in the paid versions of the Alibre Design product family. Alibre Design Xpress equips the person needing basic 3D design capabilities. 
Easy to Use and Learn
The genius of Alibre Design Xpress lies in its inherent ease-of-use. Those that are new to 3D will find the tutorials, help and user interface intuitive to learning how to build 3D designs. Those that have used 3D CAD previously will be delighted at the functionality and richness of features. 
Built-in Training
Alibre Design Xpress has a rich set of integrated tutorials that you can use to learn the product quickly. These are the same tutorials included in paid versions of Alibre Design. Furthermore, you can opt to attend online training classes a-la-carte or with a subscription. Or you may order a product or training manual for self-guided study. For a full list of features, visit the developer's site. Those that are new to 3D will find the tutorials, help, and user interface intuitive to learning how to build 3D designs. Those that have used 3D CAD previously will be delighted at the functionality and richness of features. Version 8.2 SP2 may include unspecified updates, enhancements, or bug fixes.