Small Tangent 2 Points Arc


New here. But not to SketchUp. First version I’ve used was SU6 I think.

I have recently upgraded to 2023 Pro. And I’ve noticed something weird.

Make a square of 10 x 10 mm.
Pick a corner.
From the corner draw a line of 2.5 mm following one side of the corner.
Repeat for the second side of the corner.
Select the 2 point arc tool, select 12 segments for the arc.
Pick one of the 2.5 mm segments’ end point.
Pick the other end point.
The displayed arc curvature turns pink as it is tangent at vertex.
Click to create the arc.
The arc does not appear.

Repeat the same with a 3 mm rounding and it does work.
Repeat the same with a 6 segments setup for the arc tool and it works.

In past versions there used to be a message informing the user that the number of segments was too high for the desired arc. But now that info line is gone and you are left wondering… what’s going on.

Thank you.

The missing notification message is a bug in 2023. I noticed it too.


When I want try and make small arcs, I make the smallest that will be successful then offset it to get an even small arc. For some reason offset will manage a smaller arc. Has anyone noticed that.

Or if you are working on a component - copy it to the side, scale the copy up 10x or 100x and make your arc - it will be drawn properly in the original, then delete the copy.

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What are you modeling that is so small? How will you use the model?

The safest way is to use meters instead of millimeters. This will overcome the small edges problem.

Then, when done, scale down by a 1000 factor to get the exact dimension that you want.

Hi all thank you for your replies.

That’s the only thing that irked me slightly. I know that sometimes things like that happen, but when that is the case I’m used to getting a message telling me that my arc has too many segments for the size. Took me a good 10 mins to suss it out on my second model. For my first model I changed the geometry to compensate for it.

Thank you for the suggestion, I’ll try to remember it next time I’m in a bit of a bind. For the time being I’ll try to remember not to use too many segments for small arcs.

At least for the time being, I am making models merely because I like making them rather than making them for something particular. I do technical drawings all day. Doing my own models helps me unwind. And Sketchup is SO much nicer than SW.

Thank you for the suggestion. I will have to have a look at that. This is actually one of the few times when I have chosen mm as a unit. I usually work in m but I thought that for a change it’s easier to type in 1 instead of 0.00. I’ll see how it behaves in m next. Maybe tomorrow.


That’s a good thing. I do the same thing. I have been modeling a lot of machine parts, steam engines, and other mechanical things. For those things I set units to meters and work as if they are inches or millimeters. That makes it easy to get around the tiny face/short edge limitations and make smoother looking curves. You can do as Jean suggests scaling up and back down–I do that sometimes for small objects like cabinet hardware used in the furniture plans I do commercially. For the mechanical objects I rarely bother to scale them down. Even if I’m 3D printing them I don’t scale them down as there’s no need. Look at the Sleepless Night thread in the gallery or the link in my profile to see examples.

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I am not suggwsting to type 0.01 m instead of 10 mm. You will get the same problem.

Type 10m for 10 meters, etc.

Then, when done scale by 0.001.

SU has problem creating edges smaller than a certain limit.

However, once the geometry is created, it is preserved when scaled down.

Thank you for the replies.


I have stopped doing it for a while now, but I’ve missed it and modelling for work isn’t quite the same. As for mechanical things… I’m afraid I’m not that gifted in that department. At least not if those things are supposed to work or to have worked at some point in time.

And yes, what you say makes sense. It is indeed easier to work on a larger scale model. Yesterday it took me about half an hour to clean up the intersection geometry between two bent metal pipes with a rectangular profile and filleted corners. No wall thickness. I cursed myself for having forgotten how tedious that is but then I put in the time nonetheless because that was the design I wanted :P.

I’ll have to test the scaling down thing at some point. Although for now, I think I can get where I want without it. While SW can occasionally put in fillets of 0.0625 or even smaller (yes… I sometimes use those tiny ones on bolt threads… not because I have to but merely because the renderings look so much better when you do :P), but realistically speaking, unless I am working on really tiny objects, like jewelry, then I don’t need fillets smaller than 1 mm. I remember I did do some rings years ago and for those I worked in m. I don’t 3D print, but I know that the printers have software that scales down things pretty well.

I have looked at a couple of pages of your models. Impressive. I wouldn’t do it in SketchUp if they paid me to though :P. Or maybe I am just spoiled by the tools Inventor and SW have for mechanical things. On the other hand, I’ve never actually looked at SketchUp plugins that would make this easier, since I’m not a mechanical person.


I know what you were suggesting. And I know that in doing so I would most certainly run in the same type of problem. The reason why I mentioned that is that I haven’t used mm templates at all. And was thereby implying that the behavior might be related to the template itself.

I’ll test the scaling down thing at some point. At the moment I’ve found out that the issue was caused by the number of segments in the arc. Too many segments for the small size. So next time I’ll remember to check how many segments I actually need for the arc. :slight_smile: