Introduction: How to Measure a Corner's Radius Using a 3D Printed Tool

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The world is filled with millions of different objects all with different shapes, angles, lengths, heights, widths, surfaces, depths, volumes, geometries, etc… You get the point. There are many different ways of measuring all of these different objects. Here we will focus on measuring rounded corners on physical objects. This can be a difficult task without the right tools.

Our Mechanical Engineering Team at Jaycon Systems creates, reverse engineers, and tests hundreds of hardware projects every year, so in order to make our lives easier, we came up with a simple 3D printed tool to help measure the various radii (believe it or not that is the plural of radius) of the things we work on. We hope we make your life easier as well by making these files available to the public.

Step 1: Step 1: Understand How Measuring Radius Works

Measuring rounded edges or corners of an object can be a difficult task. Most people approximate by using a ruler or caliper to measure where the curve starts and where it ends as seen in the first picture with distance A.

Corners located inside a physical object — a small container for example — as seen in the second picture can be even more difficult to measure and estimate. If someone is designing an item to fit up to these measurements, it can become a tedious trial and error game.

Step 2: Step 2: Understand How the 3D Printed Tool Works

We have used some of the measuring tools available out there, but we have found that most of them aren't suitable for tight spaces since they have a long handle that doesn't fit inside the piece we are trying to measure.

So in order to fix that problem, we created a set of plastic slivers that look similar to crescent moons. Each piece has the same radius on the inside and outside of the part, so you can measure both the inside or the outside corner radius of a part using the same piece.

The pieces are as small as 5mm all the way up to 40mm. If you need bigger sizes, you are welcome to make them your own as they are pretty easy to create with a 3D software. We believe that these will get a much closer if not exact radius measurement compared to using a caliper to guesstimate.

Step 3: Step 3: Download the STL File and 3D Print Your Tool

The STL files are set up as a group and also individually — in case you lose one, you can reprint it separately.

Download the STL files here.

Step 4: Step 4: Using Your Tool and Working With Corners That Are Only Partial Matches

Take a moment to check the next steps and see how these measurement tools work to measure radius. You will notice that at times an exact measurement cannot be taken as seen in some of the images below — it may be one size too large or one size too small, so the true size will lie somewhere in between.

In the first picture, you will see that there is a slight gap in the middle of the 14mm tool as we push it on the corner we are trying to measure, telling us this size tool is slightly too small.

As we use the 16mm tool instead, we still see a gap on the right side of the tool, which tells us that this tool is slightly too big. We would then feel safe to say that the correct size is an average of the slightly larger and slightly smaller tool at 15mm.

In the last picture, you see that the 38mm tool is a perfect match to what we are measuring, so we are happy to write down the exact reading of this tool as the radius.

We hope you enjoyed this tutorial and found the tool helpful. If you 3D print your own tool, please snap a picture and hashtag us at #jayconsystems so we can see how useful it was for you!

Who is Jaycon Systems?

We specialize in bringing products to life by offering a complete service line that takes product concepts to mass production. Our offerings range from product and electronics design to prototyping and manufacturing. We apply our knowledge of technology to most markets, among them consumer electronics, computer hardware, marketing/multimedia, and environment. With our entrepreneurial spirit and as a rapid-prototyping firm, we believe in building products right the first time and introducing them quickly to market. For more, visit