Transferring measurements of a arc from a physical object to 3d?

If I have a physical object with a arc that I want to measure what are some ways to go about it? I can trace it onto paper, find the center point and go from there but I’m guessing there are other ways I don’t know about yet. Thanks

What is the object with the arc and what do you have for tools? You could likely measure the distance between endpoints and the height. Then draw an arc with those dimensions.

Do you know for a fact the arc is really an arc? That is, it is part of a circle? If that’s important, you should check that.

Just wondering in general, but let’s take a refrigerator door hinge cover for example. It is something I was thinking of modeling just for practice.

As for tools I have what i would call some basic drafting tools and a digital calipers.

No, not really haha. How do I know for sure?


For something like this, I generally take photos of the different views I would need to re-create it in SketchUp. I usually take them about 3 or 4 meters away with a zoom lens to reduce the parallax. If it’s small enough, I sometimes use a flatbed scanner to get a good image. Using calipers (or even a ruler), you can adjust the images/geometry to get a good fit. Using this approach, it doesn’t really matter if a curve is a true arc or a sequence of arcs (or other). Sometimes some reverse engineering is required for precisely locating screw holes, bosses, etc., but the importance of exactness is dependent on the purpose of your model.

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Depending upon how accurate the copy needs to be, you could reverse engineer it as Jim suggests. Or you might put it on a scanner and trace the resulting image. I did that for the back plate for this drawer pull, for example.

For that piece it probably doesn’t matter so much if the curve on the end is really a true arc or not. You could figure out if a curve is a true arc by using a square although on a small curve like that, it would be tough. You could assume it is a true arc.