Hello, guys! Bark here from Quadraflex.de.
Metal objects are often machined with a milling machine. This results in different texture gradients in the different axes of XYZ. Milling aluminium also has a special feature. This results in additional iridescent surfaces because the aluminium immediately gets a transparent oxide layer. (Example in the zip file)
My metal materials are procedural (no textures) and are aligned and separated according to the axes. Metal X, Metal Y, Metal Z, Metal fine (as an example of a finer gradation at an edge). See example objects (open surfaces in editor)
The upper material gradient in the Node Editor represents the material/axis and the lower material gradient represents the additional material/axis. Iridescence that can be mixed at the end.
I would have liked to have offered circular (editable diameter) structure lines in Z, like a milling cutter creates them (see https://www.vdi-z.de/2015/Ausgabe-12/Werkzeuge-Spanntechnik/Ramping-Fraeser-steigert-Standzeiten-bis-zu-200 ), but I didn't manage that. Maybe someone has an idea how to create editable circular rings in the Node Editor to simulate all possibilities of milled surfaces ?
ALs HDRI Backgroud I got couryard_2K.hdr from HDRiHaven used (thanks again) .
Some other settings based on Curtis Holt (Thanks!)