Why does changing sketch plane move sketch on another axis

[Julie_7]

I started with a sketch using the edge of an object as the sketch plane, I think. It might be that the sketch was on the origin Y plane.

Is there a way to determine the current plane for a sketch?

Here you can see that the points of the sketch are on the top edge of the body. The edge of the body is on the Y plane of the origin, so I can't be sure if I originally selected the edge of the body or the Y plane when starting the sketch.

I decided that I wanted the sketch to be offset back from the edge of the body. I created an offset sketch plane from the edge of the body.

After resetting the sketch plane, this is what I end up with.

The sketch has shifted to the left and up, in addition to the X shift to put it on the new sketch plane.

Why?

In order to fix the sketch I edited it and expected to be able to just make the corner of the body coincident with the point on the sketch that had been there previously. The problem is that after selecting slice in the sketch dialog, the projected point is not selectable. While reproducing this, I just discovered that by hiding the sketch plane that I can select the projected point. The view while in sketch mode shows all the details and what I would like to know is:

Where did the green lines come from?

Why is there a circle that looks like a shifting of the origin?

You might need to zoom the image to see the circle that looks like an origin shift.

Because I cannot constrain the point of the sketch to the corner of the body because of existing constraints, I tried to remove the existing constraint.

I never know which of the constraints to remove. If I remove the wrong one then my rectangle is no longer connected at this corner. In this case when I removed the left most one, two were removed. Also, I have a hard time getting it to even show. Clicking on the point most of the time does not show the constraint. Sometimes I see the single remaining coincidence.

I find the behavior confusing and hope one of the forum experts can help to explain it.

Thanks!

[SaeedHamza]

Could you please attach the .f3d file so that we can take a closer look?

Also, when you said 'resetting', did you mean that you created a new sketch, because you can double click the same sketch plane from the timeline and see/edit it's reference

[HughesTooling]

Redefine sketch plane is pretty useless and should be avoided. As you've found the orientation of planes can be different so your sketch can rotate or mirror. and another big problem is any projected geometry is converted into normal locked geometry (green) without warning so your sketch is no longer parametric.

I've started to avoid sketching on faces and use planes instead as you can usually move the plane with the sketch without destroying the design. To help with this someone has created a Add-In that creates a plane and sketch from a single selection, see post here on API forum. Scroll to bottom of thread for latest version.

One thing to note from the description of what you were trying to do is you could have left the sketch where it was and used Start and set an offset.

Mark