Dimension to center of a circle?

[Steve]

I need to dimension to the center of a circle that is not viewed straight down the hole. In other words, it shows as an elipse in the view I want to dimension it.

How can I do this?

Steve

[May Kung]

I don't think you can catch that center in Annotation. I had a similar problem when trying to dimension to an arc's center, as it was (inexplicably) converted into a spline instead of an arc.

[John Scheffel]

When you layout a round hole at an angle I think what you end up with in Annotation is a spline, even though it looks like an ellipse. Splines don't have a center, they are defined by control points. If you right click, select Show Settings, then turn on Vertices you will see the points that define the spline. On true circles you will see the center point as a diamond.

I don't think dimensioning to an angled view of a hole is a standard practice, typically it would be dimensioned in a side view or an auxiliary view looking straight down the hole. If you dimension to an angled view it only defines where the hole intersects the angled face, not the center along the entire length of the hole.

However, if you want to do it the only way I know is to create some geometry which represents the center, either a point or a line, then dimension to that geometry. This will have no association to the hole in the 3D view, so if you move the hole you need to manually move the geometry.

[John Scheffel]

Originally posted by May Kung
I don't think you can catch that center in Annotation. I had a similar problem when trying to dimension to an arc's center, as it was (inexplicably) converted into a spline instead of an arc.
You might try this command to see if it fixes this problem.

(setq docu::*docu-blend-replacement* t)

It is supposed to force blends to layout as arcs in Annotation. We got this from CoCreate a long time ago, so I don't know if it's still applicable. As far as I know it only affects blends, it may not work for other cylindrical surfaces.

[May Kung]

Hmm. Thanks for posting that, John. I'll just add it to my list of things to test out when I have a few spare moments (sadly, the list has hit 21 and is *still* growing :().

I haven't seen this happen in quite a while, as I almost always have normal views, so I will have to dig to find a drawing with this problem.

[Steve]

I don't think dimensioning to an angled view of a hole is a standard practice, typically it would be dimensioned in a side view or an auxiliary view looking straight down the hole.

:) Yup. On my drawing I did in fact dimension it in the plane of the actual hole, but for some reason the manufacturer wanted dimensions locating the holes in a different plane.


However, if you want to do it the only way I know is to create some geometry which represents the center, either a point or a line, then dimension to that geometry. This will have no association to the hole in the 3D view, so if you move the hole you need to manually move the geometry.

That is exactly what I ended up doing. I hate "manual edits" to views because anyone in the future who comes along and makes a change to the model will not know what "land mines" are lurking on the drawing that they need to manually update.

(setq docu::*docu-blend-replacement* t)

It is supposed to force blends to layout as arcs in Annotation. We got this from CoCreate a long time ago, so I don't know if it's still applicable. As far as I know it only affects blends, it may not work for other cylindrical surfaces.

If this is the tool I am thinking of, what it does is projects any non-circular blends onto the view so that they can be dimensioned as true radii. Unfortunately, from my expreriments as I recall, the projected geometry is not associative to the model, so you are back to the above problem again - any change to the model does not get reflected in on the drawing.

Steve