If you want to use the project as-is, with the existing dimensions, all files needed are already generated and included as stl and svg.
What follows are some brief notes on how to customize the design for your own needs.

Note;
  In the text versions are replaced by * as the file versions change in future updates.
  At the time of writing I use OpenSCAD 2016.05.12.


How to customize the source code
--------------------------------
Open MJ189-HandWheel-*.scad in OpenSCAD
  Customize to your liking.
  It is mostly parametric within each module, but not as an assembly. This means that if you change the dimensions of a part (module) you will have to adjust the position (translate) in the assembly accordingly.
  F5 to preview.

  Take note of the console output "Outer diameter of scale ring:"... You will need to enter it later in the OpenSCAD script for the generation of the printed paper scale.
  In the published version the value is 34. This number will change if you change the related dimensions and will have to be entered when generating the scale.

  In the call for the explode_assembly module you can put ! in front of the the individual parts to render each one by one for stl export.
  F6 to render
  Export the individual parts to STL
  Slice
  3D print!


How to generate the paper scale strip
-------------------------------------
Open MJ189-HandWheel_scalestrip-*.scad in OpenSCAD
  Change "scalering_diameter=34;" to the value from "Outer diameter of scale ring:"
  The expression "length=(3.14*scalering_diameter)+0.5;" defines the length of the scale strip.
    (The +0.5 comes from finding that the theoretical length was a bit too short when wrapping the final paper version around the scale ring. You may need to change this to match your conditions.)
  F6 to render.
  Export to STL, MJ189-HandWheel_scalestrip-*.stl

Open MJ189-HandWheel_scalestrip_2Dprojection-*.scad in OpenSCAD
  Make sure "import("MJ189-HandWheel_scalestrip-*.stl");" refers to the correct STL-file, exported earlier.
  F6 to render a 2D projection.
  Export to SVG, MJ189-HandWheel_scalestrip_2Dprojection-*.svg

Open the SVG in your favorite vector drawing program
  I use InkScape, https://inkscape.org
  Import MJ189-HandWheel_scalestrip_2Dprojection-*.svg, drag-n-drop works fine
  Position it on the page
  My own preference;
    Set fill color black
    Set line width to 0.00
  Duplicate it depending on how many you want
  2D print on laserjet/deskjet/... printer


How to apply the scale to the scale ring
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Cut the scale strip out and wrap it around the body of a pen to get it to curve naturally and then unwrap it.
Attach the end of a roll of sticky tape to the pen body and turn it a few centimeters.
Then put the scale strip between the pen body and the sticky tape and continue to turn it until the whole label is wrapped up around the pen.
  Be sure to start with the end of the scale which is missing a number.
  That line can be used to aid the alignment and verify that the printed scale is correct.
  0.6 should line up perfectly with the numberless line.
Unwrap it from the pen and cut away all sticky tape around the label, leaving some tape at the ends so that you have something to start with as well as some overlap at the end.
Dab a few drops of super glue/cyanoacrylate on the back of the paper strip and wrap it around the plastic ring. Done!