Hobbyists do often need to find the center of a circular object. This device helps them to find the center point of circles up to 200 mm diameter.

First, put the circular object on a tangential position to perpendicular side arms of the device and trace a line with a pen through the slot of diagonal arm.

Secondly, rotate a little bit the circular object and repeat the same operation.

These 2 lines intersect each other on exactly the center of the circle.

It takes 01h.14min. 29sec. with 0.5 mm layer height, 20 % infill, 60 mm/s speed. I used 0.75 mm PLA.