Reply To: Is this hard surface geometry ok?

[plasmavoyage]

The outer ring is not needed when you work with mechanical parts like that, because you don’t use subdivision modifiers. 

If you are supposed to deliver a model of a metal piece like that for a a manufacturer to work with and for example laser-cut it out of metal sheets, you would work with splines to get smooth curves. 

The manufacturer gets a clean shape that he can enter into his software and his machines can start cutting that shape into metal sheets. In this case, if you want to box-model that metal piece you have to either take the fall with the blocky ring or you use the boolean modifier to create an almost perfect circle for the ring but suffer a chaotic topology around the ring part. 

The difference between a high poly tube being cut into that part to create a smooth ring as opposed to using a subdivision modifier is that the subdivision modifier does that to your entire mesh and is harder to control. 

While the boolean modifier will create hundreds or thousands of additional polygons as well, they will all be connected to the next-closest vertex that is available, limiting the amount of uneeded additional polygons to a fraction of what a subdiv mod would create. 

You can of course control the subdiv mod too by using vertex groups but usually that will end up in a very similar result as the boolean modifier would give you.
So my advice on this would be to either take the fall with the blocky ring or use splines.

I’ve worked in a media agency for 4 years and one of my last clients there was a company that sold and produced mechanical parts from large to small scale, very similar to these ones. 

They had a price catalogue that had every single part listed with exact descriptions, measurements, material, resistance etc. along with a technical drawing that would be similar to what you are doing right now, just without a wireframe (so all built using vector files) and a 3D rendered image. 

The way we did it was we used Adobe Illustrator to create the parts using only vectors, which gave us a smooth shape with close to no hardware power required, we then imported the vector files into a 3D program like Cinema 3D or in this case Blender, made some adjustments to the vector file, gave it a thickness, smooth shading, beveling and a specific metal shader and rendered it. 

Save the image, add it into the price catalogue in Indesign and rinse and repeat for 2.000 pages. 

So like I said, splines if you want to get really technical, if not take the blocky ring for a clean topology.
Or use the subdiv mod and restrict it to the vertex group that is around the ring part.
Or use a Boolean Modifier with a high poly cylinder which will result in pretty much the same thing as above.