Here's an example of what I mean about the Loop tools, and how you can use them to make some nice shape blending for hard surface modeling.

Let's say you have a planar box shape, and you want to make a specific part of it concave, or as if a tube was booleand into one side...

You can use the Curve edges command in the Loop Tools panel for this, very easily, without messing up the topology.  Here's how.  On the side you want a concave curvature, select two points at either end, and push (or pull) them in as deep as you need the curve to be.  These points are your "markers".  They will indicate the deepest part of the curved surface, so you can be quite precise and use snapping or precise measurements.  The only critical part is that you pick points that are within the area you want to make concave or convex.

Then, switch to edges, and select the exact edges you want to make concave (or convex).

Now, in the Loops Tools panel, just click on "Curve".

The result is that the edges will automatically become adjusted to the depth indicated by the vertex "markers".

This can be used, as you can imagine, in many circumstances where you need to blend planar surfaces with curved ones, without using booleans, or modeling with patch or nurbs surfaces.

The Quad Chamfer modifier can do this even easier, and all you would need is one edge loop to start, as in the image Maxxmodels posted.

Some of the shapes you posted can be done easily this way, or with similar tools in Graphite, like Set Flow.

______________________________________

My Store
My Free Models
My Video Tutorials
My CG Animations
Instagram: @luxxeon3d
Facebook: https://www.facebook.com/luxxeon