Tools of the trade: Vernier calipers

A Vernier caliper is a useful tool for measuring things precisely. The caliper shown in the following photos is precise to 0.05 mm (1/128 in).

08 MAR 2021 | Bog Photo Studio | analog Vernier caliper

Some guides to the identification of odonate larvae and exuviae are measurement intensive. A caliper can be helpful for making measurements of a specimen quickly.

08 MAR 2021 | Bog Photo Studio | analog Vernier caliper (close-up)

Carolina Biological Supply Company sells both analog and digital calipers. Analog calipers are relatively inexpensive and work well. Digital calipers can cost at least five times more than their analog counterparts.

Carolina sells two models of analog Vernier calipers: one model is made of nickel-plated steel; the other is made of plastic. The metal caliper has sharp edges and points that can scratch surfaces easily; the plastic caliper won’t scratch most surfaces.

The metal model comes in a plastic pouch; the plastic model doesn’t. Advantage metal model, right? No! Both the metal caliper and its plastic pouch are covered in some type of lubricant that is both unnecessary and a chore to clean off the caliper. Can you tell I prefer the plastic model?

Learning by doing – How to read the Vernier scale

How to Read a Metric Vernier Caliper by (7:01) is an animated video that explains how to read the Vernier scale of an analog caliper. Watch the video, then test yourself to see whether you can determine how far the bigger jaws of the caliper are spread apart (in mm), as shown in the preceding close-up photo.

Be careful — the Vernier scale shown in the video is precise to 0.02 mm while the one shown in the photograph is precise to 0.05 mm. Here’s a hint: The jaws of the caliper are slightly more than 11 mm apart.

Please submit your answer as a comment on this blog post. Relax, you won’t see any spoilers because all comments must be approved by the blog administrator. (Hey, that’s me!)

Post update

The answer key for the caliper quiz is now online.

Copyright © 2021 Walter Sanford. All rights reserved.


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5 Responses to “Tools of the trade: Vernier calipers”

  1. Mike Powell Says:

    My eyes are not super-calibrated, but it looks like 11.1 mm to me.

  2. Jimmy Dee Says:

    Well actually looks to me like 11.125 mm as each of the lines at 11.10 and 11.15 are ‘very slightly’ off. But you are prob looking for an answer like 11.10 mm 🙂

    • waltersanford Says:

      When I used Adobe Photoshop to annotate my close-up photo of the caliper, I drew two vertical guidelines. The guideline for 11.15 mm is aligned perfectly with the tick marks on the main scale and Vernier scale.

      • Jimmy Dee Says:

        Great! I do have a steel and plastic vernier. I had originally bought the plastic to measure baskettail female adults, hoping to see a difference in size, to see if that would help to ID them. The plastic ones are nice and light and cheap. I also have digital vernier and micrometers … but that was for my 35 years as a machinist. Thanks for that nice post!

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