To Create Centerlines and Center Marks

1. Click Dimension menu Dimension Style.
2. In the Dimension Style Manager, select the style you want to change. Click Modify.
3. In the Modify Dimension Style dialog box, Symbols and Arrows tab, under Center Marks, click Line.
4. In the Size box, enter the length of the centerline overshoot. Click OK.
5. Click Close to exit the Dimension Style Manager.
6. Click Dimension menuCenter Mark.
7. Select an arc or a circle.