Open Source 3D design tools?

[jfkansas]

Fusion 360 should be good at that.

Try Design Spark Mechanical. I use it sometimes.

Another that I use is Emachineshop.com. They have a free 2d program with 3d preview. Sometimes I do my sketching on there since it is simpler to move things around if you just want to play with shapes. When I am satisfied with the design I will export a dxf and import to Fusion 360.