I often model separate pieces and modify them with boolean operations to get to a final result. I'm stuck with a quarter of a cone intersecting with a hollowed cube (think of an inverted tray). My goal is the union of the cone and the smaller portion of the cube/tray. In other words the cone is larger than the diagonal of the tray. I'm not getting desired result in Blender 2.77, but I really think I'm missing a step somewhere. If you don't have and answer for that, how about a link to steps to manually do it? It really is simple, but I'm afraid I've been away too long. Thanks for your thoughts. Looks like it worked - Nope
The problem is that your mesh is non-manifold, meaning you have holes on its surface, it can't boolean properly. To fix that, go in Edit mode, select the whole mesh, go in the Mesh menu > Clean Up > Fill Holes. Also you should recalculate the normals with a ctrlN even if it seems to work with bad normals. Then boolean with the Union mode and it works.