I'm trying to create a 3D model of a key in Blender made from a single cylinder object only. But I'm having trouble to think of a way of how to extend a round handle from the cylinder as seen from the image. I'm still a beginner and I haven't learned all the modifiers yet, so maybe there is a technique of how to achieve this.
Extrude the cylinder and scale up the new face on the X axis (s+x), then extrude straight, after that extrude it again but scale it down on the X axis. Then select the center face on both sides and make a hole with "bridge edge loops". Finally use subdivision surface and use edge loops/or edit the mesh to refine the shape. It should look like something this:
If you want to get persnickety about the exact shape and profile of the key's loop, and have control over curvatures in the transition to the shaft, this workflow might save work, tweaking...
- You could start with a Curve > Circle, its control points set to 'Free' so you can scale them in X and Y, object-bevelled with a profile curve of your choice. (Here, a rectangle)
- Convert a copy to a mesh. andCtrlR cut loops into the sides, and scale the front vertical in Z, to accommodate..
- .. an I inset of the front faces, beginning to approximate a circle..
- use Loop Tools > Circle to round the inset, and set the shaft radius
- Move the inset out a bit, and E extrude it further
- V cut the mesh down its axes of symmetry, and delete 3/4, so you can save work while ..
- .. bevelling edge-loops and tweaking vertex positions, working under a mirror in 2 axes, and possibly a couple of levels of subdivision, with a metallic matcap, so you can see the effect of small adjustments.
For making tiny tweaks, I often find it helpful to use the Z of the 'Normal' transform orientation, and be ready to ShiftAltZ turn viewport overlays on and off, while working.
Your reference topology would be nearly impossible to edit. By contrast, adjustments to 1/4 of a quad loop topo are a pleasure...it will be easy to change the shapes to exactly what you want.