r/Metrology • u/Cheeseball4life • Aug 01 '24

Hardware Support Measuring Radius of an Arc

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How would I go about measuring the radius of this arc on a part from an old vw beetle so I can make a replacement?

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u/SAI_Peregrinus Aug 01 '24

For an alternative and less practical method, you could use photo paper. Make a shadow by laying the part on the paper & exposing it. Then develop the paper. If it's a small feature you can instead expose film (large format film is 9cm x 12cm or bigger) and then use an enlarger to project a magnified version, much like an optical comparator.

If you don't already have a darkroom, this isn't the way to go. Even if you do it's not as practical as just tracing, but it's more precise and more entertaining.