No need to waste money on expensive mechanical pencil, when you can print a fully printable mechanical carpenter pencil.
Uses 2.8mm lead.
Might be a little rough at first due to layer lines, but you can sand the bottom side of the button/pencil holder assembly and/or add some grease. I personaly just played with it till it became smooth by just sliding the button up and down.
Layer height: 0.20
Walls: 4
Bottom n top: 5
Infill: 15 % Gyroid
Support: Only for Button( Pencil holder assembly)
Brim: Yes