The caliper is intended for a quick measurement for the radius; it is also very handy for the diameter for circular objects

Two sizes are available
  1. Small: ranging from 1mm to 21mm, 

  2. Large: ranging from 20mm to 52mm, 

subject to the printer tolerance, I would strongly recommend the nozzle of 0.2mm for higher accuracy 

below is the comparison between 0.2mm Nozzle and 0.4mm Nozzle.

it is clear to observe that line width is much finer with 0.2mm nozzle

User Guide

simply slide the caliper until it touches the corner of objects for measurement

the radius value is the intersection of the ruler and caliper 

Design Concept 

using basic math to quickly measure the radius of objects

this is more than a tool or gauge, it demonstrates how we could actually apply math into everyday life

  Math used in the design

   1.Pythagorean theorem

   2.Trigonometric functions

Part I: Radius Calculation

 by Pythagorean theorem, it could be derived X = 0.414R

 that is, if X is 2.071mm, then Radius is ~5mm

Part II: Measurement Tolerance Improvement

with respect to the increment of 0.414mm, it would be considerably changeling for 3D printing when taking the tolerance into account.

To improve the tolerance, one of the approach is to scale up the measurement unit

I've tested a various of length, an increment of 1.5mm is easier for reading, and also easier for 3D printers

that is, the goal is to change the relationship between X and R from X = 0.414R to X = 1.5R 

by Trigonometric functions, the angle is determined 73.97 degree