Knurling is normally conducted on a lathe and is part of the manufacturing process adding a pattern such as cross hatching or bumps to a surface to give it a finish look and allow the surface to be gripped easily. It’s something to do at the very end like fillets and chamfer - youtube

• FreeCAD - Circular Textures/Patterns
• Knurling in FreeCAD
• Sketch on Curved Surface / Faces in Curves workbench. Celtic Ring
  • Mapping text to a curve surface