Curves not behaving accurately, shifting

Hi. I am a new Rhino user having great success so far this week but I’ve just noticed my components are shifting. I am working in cm to a 0.0001 unit tolerance. I am creating an object which would be machined from several material blanks and then assembled. Each block material is a single layer.

I have one rectangular surface for example. I will use it’s edges, locking to end points, to create another one in another layer which will be machined from a different material. The edges are flush. I may then go on to extrude, create some advanced shapes etc on the second surface only later to find that when zooming in very close on Perspective View, the bases no longer match up, with even a 1mm(!) offset. I have been mirroring things along the centreline fairly often but I’m noticing they sometimes wont join up exactly in this same way. Yes the project is perfectly symmetrical across the centreline. I can go in and Move to point to fix this now I know it isn’t always landing perfectly…but even then I can’t guarantee it wont move by itself slightly later. Usually it’s just one end that moves, the other will stay on point.
What’s going on?

Hi Tom- It is possible to drag objects by accident - kind of click-select-drag all in one go- you can set OPtions > Mouse page to ‘drag selected objects only’ to disable that, and you can set the drag threshold on that same page very high to essentially disable dragging altogether.


You may have dragged objects accidentally. You can lock objects or layers that you’re not working on and still be able to snap to them.
…and I was typing the same thing as Pascal, but he’s faster…