since this should work for several versions of SE and as it could be done here - also ST8 - MP5
there might be 2 reasons I can imagine to ot be able creating these center arc:
The arcs you see on the screen grab are pipework elbows created in XpressRoute then shown on the SE draft so no it would no be a spline from 3d geometery, any ideas ?
OK, if this is a pipework then the centerlines should be created automatically when creating the draft view.
There is an option in the drawing view wizzard wether or not centerlines of pipes should be displayed or not.
If this option is ON then the centerlines come by itself
OK, what I have seen is, that if the pipe main plane is not exactly parallel to the viewing plane, then the center arc function will not select the second "arc" since it will not be exactly an arc or the center of both is not exactly the same
I have tested this with a 5 degrees rotation of the view and You can see that the centers are different about 0.01 mm
thanks Woldgang, I appreciate your help with this, the strange this is some other pipe elbows on the draft do allow me to add the arc centerline, not quite sure what happened to that one
and if it is a pipe and the option "show pipe centerlines" wasn't set yet from the beginning then You can go to view options - show all and show centerlines ON