Is there a tool or custom setup I can use to measure the center of a small, shallow bend? The arc length of the bend would be too small for a three-point radius gauge (around 5 mm).enter image description here

  • 1
    Do you have a bent "flimsy piece of thin plastic" whose bend radius you're trying to measure, or are you trying to put a specific bend radius into said straight piece of plastic?
    – FreeMan
    Dec 2, 2021 at 13:05
  • You could try this: Google: "Circle radius and centre calculator given 3 points". It assumes you can plot three points of the arc onto graph paper. Dec 2, 2021 at 15:42

1 Answer 1


What will work depends on the angle/length of the available arc and your required accuracy.

You could try gauging it against objects of a known radius/diameter, e.g. washers, bottle caps, etc...

Hold your arc against the reference object, shine a light from behind, and see which object produces no or the smallest gap.

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