Associative Center Lines in AutoCAD 2017

By Bill Fane

AutoCAD 2017 introduced a new associative functionality in the form of associative center lines. This can be very helpful when working with dimensions. It involves two commands:

  • CENTERLINES: Prompts you to select two lines. AutoCAD then draws a centerline midway between the two lines using a long-dash–short-dash line style.
  • CENTERMARK: Prompts you to select a circle or an arc. AutoCAD then draws two centerlines that cross at the exact center of the circle or arc.

Now comes the magic part. Centerlines created using these two commands are fully associative to the lines, circles, or arcs that were used to define them. If you move an arc or a circle or change its radius, or if you move either line or either end of either line, the centerlines obediently follow and remain properly centered.

Associative centerlines are automatically placed on a Center lines layer with a Center2 linetype override. If this layer doesn’t exist, AutoCAD automatically creates it with a white/black color and the Continuous linetype. If this layer already exists in your template file, AutoCAD uses the color you specified, but ignores the linetype assigned to the layer and applies the Center2 linetype override.