Reading A Vernier Caliper

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I got a plastic vernier caliper for measuring watch parts. I got a plastic one because it’s (1) cheaper and (2) it will not scratch the watch.

A caliper is a device used to measure the distance between two opposite sides of an object. A vernier scale is a device that lets the user measure more precisely than could be done unaided when reading a uniformly-divided measurement scale (such as a ruler). A vernier caliper is therefore a caliper equipped with a vernier scale for precision measurements.

It has a main scale (in this case, in mm), a sliding vernier scale (in this case, with graduations that correspond to 0.05mm), inside jaws (upper, smaller jaws on picture) or the outside jaws (lower, bigger jaws on photo).

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The inside jaws is for measuring the distance from inside of objects like lug widths (inside distance between the lugs of a watch). The outside jaws is used for measuring from outside of objects like length, width, height, case diameter, and lug-to-lug distance (distance between the tip of the top lugs to the tip of the bottom lugs).

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Simply slide and position the jaws lightly on the object to be measured and read the scale. In this case, the “0” index on the vernier scale points a bit over 41mm on the main scale. How much is a bit over? Find the index on the vernier scale that lines up with the index on the main scale. In this case, it’s 2. Thus the distance is 41mm + 0.2mm or 41.2mm (with a ±0.05mm error).

That’s all there is to it :)