By Martin Phelps
Adding centre marks to a circle or arc has always been a simple matter of accessing the “Centermark” command and selecting the circle or arc.
In AutoCAD 2017 the centre marks are now associated to the circle or arc from which they are created.
The “Centermark” command is located in the “Dimensions” panel of the “Annotate” tab as show in Figure 1 or by typing in “Centermark”.
Once the command is activated, select the circle or arc, the “Centermarks” are created as shown in Figure 2.
Since “Centermark” is now associated to the circle or arc from which it was created, should the size of the circle or arc change the “Centermark” will also change. As shown in Figure 3.
Selecting the “Centermark” will display grips enabling the length of each line that makes up the “Centermark” to be stretched independently, as shown in Figure 4.
The “Square” grip controls the “Centermark” “Length” for each line, and the “Triangular” grip controls the “Centermark” “Overshoot” for each line.
The appearance of the “Centermarks” are controlled by a number of new system variables.
“Centerexe” - sets the length of the “Overshoots” for the centre marks, or how far the “Centermark” line extends passed the circle or arc from which it was created. The example on the left in Figure 5 has a value of 30, while the example on the right has a value of 3.5 which is the default setting.
The “Overshoot” can be changed by using the “Centerexe” command, and updating the “Centermarks” by typing in “”Centerreset” and selecting the “Centermarks”, both of these commands are currently type-in.
Centerlayer - sets the layer on which centreline are created.
Centerltype - sets the line type used in the creation of “Centermarks”.
Centerltscale – sets the line type scale used by “Centermarks”.
Centercrosssize – sets the size of the central cross for “Centermarks”. In Figure 6 the circle on the left has a “Centercrosssize” value of 0.5x, and the circle on the right has a value of 0.1x.
Centercrossgap – sets the line gap between the central cross and the extension lines in “Centermarks”. The circle on the left in Figure 7 has a “Centercrossgap” value of 20, and the circle on the right has a “Centercrossgap” value of 5
The “Overshoots” for all four centre lines, the “Cross Size” and “Cross Gap” can also be changed by selecting the “Centermark” and accessing the information via the “Properties” dialogue box. As shown in Figure 8, allowing different values to be set for each line.