Accuracy Issues

I know it’s been said before and I know sketchup is 100% accurate, so why is the model I’m working on constantly inaccurate?
I’ve switched off length snapping
I’m using a 1mm tolerance
I’m using the tape measure
I’m typing in my dimensions
I’m making my entire model from separate components
…But still on closer examination plenty of items are not marrying up 100% (They are off my a couple of mm)- What am I missing here?
Also would like to point out that when I create a component and set it’s own axes the component moves fractionally and has a bounding box that is not aligned with the item, making it tricky to line up again.
Someone please tell me the secret. Sketchup is so intuitive but it’s suddenly gone counter intuitive and unreliable.

Thanks in advance

Hard to give you any guidance without seeing your model file.

What version of SketchUp are you using? Please complete your forum profile with that information.


Here is the piece I am working on, I’m on the latest version of sketchup


Ceiling Piece.skp (159.9 KB)

in your list, using the inference system is missing

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Pretty certain I am using the inference system as well

So far what I see in regards to “inaccurate” dimensions looks like it is down to simple trig and some probably incorrectly drawn angles. How did you lay out the triangular elements?

For example in this component:

There’s no reason you shouldn’t be able to draw a perfect equilateral triangle. Here in your model I’ve done that very simply and precisely using the Polygon tool.

This isn’t meant as a put down but what I see in your model just looks like some careless modeling. It might help if you increase display precision. That won’t make your model more precise but it will help you see when things aren’t correct so you can fix them before your model gets out of hand. With a model like yours, it only takes getting the first component modeled incorrectly to throw off the rest.

As for the component geometry appearing to move when you change the axes, what are you using to guide the placement of the axes.


Fair enough! I’ll sort out the trig and see where that gets me, though can you tell me why a component would move slightly when I reset it axes?

I can see some of the slightly-off sizes and alignments you describe. To me they look like “pilot error”, but without watching over your shoulder I can’t tell where your specific defects are coming from. A couple of questions though:

  • why have you drawn the geometry so far away from the origin? Sometimes that can cause problems resolving small increments.
  • why have you oriented the model at that angle to the model axes? Unless you temporarily change the drawing axes while working, that prevents using on-axis inferences and can make it harder to align things.
  • as @DaveR pointed out, what process did you use to create the triangles? They have strange values…

Edit: I had no problem with resetting component axes, though one must be careful to get an inference on the correct object when setting the new origin.

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How are you setting the axes when you do so? Are you giving the component any gluing properties? I frequently set axis locations for components I create but I’ve never seen one appear to move when I do so.

I’m sharpening up my geometry, which will hopefully work! So thanks for help. I’m setting my axes when I create the component. not gluing, don’t know what that means?

What are you using for your references when setting the axes?

I hope you are either doing it via the polygon tool as @DaveR suggested or using other constructive tools such as the protractor, not doing trig calculations separately! There is no need to resort to math!

Also be aware that care is needed if you try to use arcs or circles to set up triangles because SketchUp represents arcs and circles as a series of edges not as true arcs. It is possible to use them accurately, but only if you understand the behavior of SketchUp’s drawing tools due to this representation.

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I’m referencing the components them selves, I’m doing it to get a bounding box that aligns and allows me to flip easily