Caliper Radius Gauge Set – Four Versions for Precise Measurement – Up to 400 mm Diameter and easy math

I needed a radius gauge, which unexpectedly turned into a small math project.

Many gauges use a 90-degree angle, which results in a factor of 2.4142… that the measured value must be multiplied by. Reducing the angle to 60 degrees naturally brings this factor down to 1, but limits the maximum object size.

To cover more use cases, I designed two additional gauges with angles that correspond to factors of 2 and 3.

With the largest gauge, you can measure objects up to 400 mm in diameter.

The gauges have a 16 mm slot, so standard calipers fit perfectly. The edges clamp the caliper lightly, so it sits snugly. I created four different versions — let me know which one works best for you.

F is the multiplication factor (Radius: R = m x F; m measured value); alpha is the opening angle; F: leg length; Rmax the largest radius that can be mearsured (probably in reality we cannot fully go to that limit, as we want the tool to make a tangent to the circle. 

For the math please check the corresponding picture.

Printing

• PETG or PLA

• 0.2 mm layer height

• 3 perimeters

• 5 top & bottom layers

• 25% infill

• Print bed: at least 22 cm × 25 cm (e.g., Core One)

Let me know what you think about it an whether it works for you.