[Arne]’s 3D printed radius gauge is a simple object; a rigid attachment for a nearly ubiquitous model of digital caliper. By placing the curve to be measured between the two arms of the device ...

The micrometer scale on the shaft of the gauge. A micrometer is a G clamp ... Mitutoyo 530-122 Vernier caliper, right: cheap digital caliper. I’ve amassed a selection of both for comparison.