Hi Michael

>> When you snap the center point of the circle on to a surface, it will take on the orientation of that surface and snaps off of that plane will be suppressed. If they were not suppressed you would not have a very natural circle drawing method because of all the snaps getting projected down to the plane cause the circle to jump wildly in size instead of moving smoothly in size when you move the mouse.

Make sence, I didn't notice it earlier so I was surprised :)

>> This suppression only happens in the 3D view, you could probably get what you want by setting up a CPlane and then using the Top plan view which will not have snaps suppressed.

Thanks for the tip, I'm not used yet about the cplane hehe

>> It could help me understand the problem some more if you could show the desired result that you are looking for.

For that example, I want redraw the 'trimmed' circle by a new one, to create some fillet manualy (using the donut boolean technic).
Sorry for the trouble, I should not post so late after a long working day :)