In Art4TransmissionColumn FreeCAD file you have to go to the Sketch046 and change the radius (default is 3,2mm) with the radius value of your choice. To do it just double click on the Sketch046 to change to the Part Design workbench to be able to edit the dimensions. Double click on the radius dimension and change it.
The same goes for the Art4BearingRing FreeCAD file, but in this case the Sketch047 is the one that you will have to modify.
Hope it helps!