Use centerlines and center marks to designate holes, fillets, and circular edges in drawing views. The program creates both centerlines and center marks on the current layer; both are attached to a view and move with it as you change the model.
You can set a default so that the program creates centerlines automatically on all Inventor link drawing views with holes, fillets, or circular edges. You can also show centerlines for individual views.
You can define the size and characteristics of the centermark with the Options dialog box. You can also define them for individual views using the Settings button in the Edit Drawing View dialog box.
The AMCENLINE command uses four system variables to determine the size of center marks and centerlines: AMCLGAP, AMCLOSHT, AMCLCM. and AMCLPAR