To set line weights
1. Click Insert tab
The Import Line Weights dialog displays the mappings in the importlineweights-dwg-default.txt file.
2. If this is not the file that you want to edit, click Load, navigate to the correct mappings file, and open it.
3. In the dialog, match the appropriate pen to the appropriate line weight (for example: Pen Number 1 to Line Weight Number 1, Pen Number 2 to Line Weight Number 2, and so on). Set as many pen-line weight mappings as desired.
4. Click OK, or to save the mappings in a new file, click Save As.
However I typically explode the detail and change the lines to Revit lines so I can then export the view to build up my Revit Detail Library.