To Set the Default to Create Centerlines Automatically (AutoCAD Mechanical Toolset)

Note: Inventor Link is available only on 64-bit systems, and it is not installed by default.
  1. At the Command prompt, enter AMOPTIONS.
  2. Click the AM:Drawing tab.
  3. Select Automatic Centerlines.
  4. Choose Apply, and then click OK. Centerlines are displayed for any view you create from this point forward.