How to Use Vernier Calipers Like An Engineer
Vernier calipers are among the most precise and versatile measurement tools in the field of engineering. Despite their accuracy, they are often misunderstood or underutilised due to their seemingly complex scales and different ways to obtain measurements. This guide aims to demystify the physical use cases of vernier calipers, teaching you how to use them accurately for various measurement tasks.
Before learning how to use vernier calipers, we recommend reading our counterpart article “How To Read A Vernier Caliper” which will prepare you for this article.
Contents:
A Quick Understanding of Vernier Calipers
Before we dive into how to use vernier calipers step by step, it's worth having a quick recap of what they are.
Calipers are precision metrology tools and come in various forms, the most popular being vernier calipers and digital calipers. They consist of a sliding scale with jaws attached that can accurately measure objects. Contrary to popular belief, both types offer similar levels of accuracy, typically ranging from 0.05mm to 0.02mm.
To put this into perspective, a grain of rice is about 0.5 mm wide, and the human eye can discern differences down to approximately 0.1 mm. Vernier calipers measure beyond this threshold, providing precision that is imperceptible to the naked eye.
While digital calipers offer ease of reading, vernier calipers do not require a power source, making them reliable and essential tools in any engineering workshop.
Types of Measurements Vernier Calipers Are Best At
Vernier calipers are capable of performing four main types of measurements:
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Outside Diameter (External Measurement): Using the main jaws to measure the external dimensions of an object such as the outer diameter of a precision screw.
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Inside Diameter (Internal Measurement): Using the smaller internal caliper jaws to measure the internal dimensions, such as the diameter of a hole.
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Depth Measurement: Utilising the depth rod to measure the depth of holes or recesses.
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Step Measurement: Measuring the distance between two steps or surfaces on an object.
Measuring Outer Diameter With Calipers
Outside calipers are used to measure the external dimensions of an object. The jaws are placed on the outermost faces of the object and clamped squarely up to give an accurate diameter measurement. Whenever possible, especially with cylindrical objects, position the jaws perpendicular to the object and not parallel. This will make sure you measure the widest point every time.
Follow these steps for accurate measurements:
Prepare the Caliper
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Make sure to clean and check the zero calibration on your caliper. Any debris or damage will give you an inaccurate reading.
Position the Object
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Place the object perpendicularly between the flats of the main jaws on the caliper for the greatest accuracy and slowly close the jaws until they make contact with the external surfaces.
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Move the object as close as possible to the body of the caliper to minimise any play in the sliding mechanism or jaws which could introduce inaccuracies.
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Avoid using the very tips of the jaws if possible as they are angled to fit inside small gaps, like between screw threads. This could give an incorrect reading without you realising by making the object off-axis.
Ensure Proper Contact
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When the jaws make contact with the faces of the object and sit flush, apply moderate pressure and wiggle the object slightly. This ensures there is no play and the object is seated correctly.
Most Important Tip From Our Engineers!
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To get the most accurate measurement of your object, it must be squared to the jaws keeping the caliper perpendicular to prevent the chance of angular errors. Any misalignment can result in inaccurate readings, especially with cylindrical objects like screws and bolts where if you measure parallel, you might not actually be measuring the widest points.
Measuring Inner Diameter With Calipers
Inside calipers are designed to measure the internal dimensions of an object, such as holes or recesses. The internal caliper jaws are inserted into a hole or recess and extended until they touch the walls of the hole. This will give you the internal diameter measurement.
The inner diameter jaws are the smaller jaws opposite to the main jaws, you can tell they are to measure inside items because the jaws are flipped the opposite way.
Follow these steps to get the most accurate reading possible:
Prepare the Caliper
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Once again, clean and check the zero calibration on your caliper as even the smallest bit of debris or damage will give you an inaccurate reading.
Position the Caliper Jaws
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Carefully insert the smaller jaws into the space to be measured.
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Open the jaws until they make contact with the internal surfaces.
Optimise Contact
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Try to maximise contact along the length of the internal jaws for better alignment. You’ll notice that most often, the entire length of these inner jaws are tapered, this means it’s even more important to measure as close to the caliper body as possible by inserting the jaws as far as they can go into the hole.
Most Important Tip From Our Engineers!
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To find the widest measurement, gently rotate the calipers back and forth along the axis of the jaws while applying slight pressure. This most often looks like rocking them towards and away from you. Rotating the caliper ensures the jaws seat correctly and measures the widest point of the internal dimension, providing the most accurate reading.
Measuring Depth With Calipers
Next up is measuring the depth of an object. This is measured using the depth rod which extends from the opposite end or base of the calipers. As the base of the caliper rests on the top edge of the object, the caliper can be extended and the depth rod drops down to take the reading.
To get the most accurate depth reading with your calipers, follow these steps.
Prepare the Caliper and Object
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Clean off your calipers making them free of debris and check the zero calibration is accurate.
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Visually inspect the hole you’re trying to measure the depth of, paying close attention to any debris that could obstruct an accurate reading. Clean any debris or obstructions away.
Position the Caliper
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Make sure the base of the caliper is sitting as flush as possible, checking that the depth rod is also squared up to the walls of the hole you're measuring the depth of.
Most Important Tip From Our Engineers!
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You’ll notice on the depth rod that there is a slight notch on the bottom.
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When measuring a hole that is squared off inside, the notch is used to avoid any bevel or small machining imperfections that could be present inside the object. Make sure to have the notch facing towards the wall of the object you’re inserting the depth rod into to get a flush measurement at the base and avoid getting a misread.
Extend the Depth Rod
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Slide the caliper down until the depth rod reaches the bottom of the hole.
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Ensure the caliper remains perpendicular to the surface to avoid angular errors by checking the base is flush with the material and the rod is aligned flush with the hole walls.
Measuring Step With Calipers
This is one of the hidden features of a caliper which most people are unaware of. It consists of using the flattened off top of the caliper, taking advantage of the top and bottom sliding parts.
By extending the calipers just slightly and looking at the back of them, you’ll discover that there is a step that appears. Using this step you can rest it upon an item, aligning the bottom step and extending the top until it reaches the surface of the next step.
To get the best measurements measuring a step:
Prepare the Caliper and Object
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Clean off your caliper and object making sure they’re both free of any debris or damage. Then check the zero point on your caliper is accurate.
Position for Measurement
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Extend the calipers just slightly to initiate the step shape on the back of the caliper.
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Rest the lower jaw's flattened off top edge on the edge where the step you're trying to measure finishes.
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Slide the caliper until the top jaw contacts the next step up.
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Keep the caliper straight and perpendicular to the steps on both axis, taking advantage of the flattened of tops and the flat nature of the extending body of the caliper.
Most Important Tip From Our Engineers!
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Maximising the surface contact between the caliper and the object will make it easier to remain squared and thus enhance measurement accuracy.
Using the Caliper Locking Screw
One often overlooked feature of calipers is the locking thumb screw feature. This allows you to take a measurement, then once you’re happy that the reading is accurate, you can tighten the thumb screw in place to allow you to “keep” that reading once you remove the calipers.
This is handy if you need to take a single measurement and refer back to it, or even for if you don’t have a pen handy at the moment, you can lock the measurement off while you go and find somewhere to note down the reading.
Take care to apply light pressure to the caliper when using the locking feature as the rotation of the threaded thumb screw inside could influence a small amount of misalignment. The applied pressure should be enough to negate any chance of this, however.
Caliper Test for Accuracy
If you're ever unsure if your caliper is measuring accurately, it's possible to perform caliper tests with precisely machined blocks known as gauge blocks.
These blocks are made and calibrated to exact measurements and allow you to perform a caliper accuracy test by measuring them to make sure the result you get is actually the size of what the block was made at.
For example, you can purchase gauge block sets that allow you to measure down to 0.0005mm accuracy which is far more accurate than any caliper.
Taking the 10.0000mm gague block and measuring across it should give you 10.00mm on your caliper reading. If you end up getting more or less then you’ll know your caliper is out of calibration.
Reasons for losing calibration are usually down to wear and tear, be it damage to the jaws, or perhaps the jaws have just seen so much use that over time they have worn down. Remember, it only takes a microscopic amount of wear or damage to give an inaccurate reading, sometimes that isn't always visible.
Hidden Feature of Vernier Calipers
Looking at the back of your vernier caliper, there is a chance that you might have what looks like a table or chart. This is usually a chart that gives you the most common imperial and metric screw sizes, consisting of their outer diameters, thread pitch or threads per inch, minor diameter and drill bit sizing to tap a hole for them.
If your caliper doesn’t have this nifty little feature, then Accu has you covered as we have a full range of these charts with every measurement you could possibly need for:
Tapping Drill Sizes & Clearance holes
Wrapping Up: Mastering Vernier Calipers
By following this guide, you should feel more confident in how to use a vernier caliper for various measurements. To gain the most accurate readings remember.
Key Takeaways:
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Types of Measurements: Calipers excel at precicely measuring outer diameters, inner diameters, depths and steps.
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Proper Technique: Use the correct part of the caliper for each measurement and maintain proper alignment.
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Cleanliness and Calibration: Always start with a clean caliper and ensure it is properly zeroed.
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Practice: Regular use will improve your skill and speed in taking accurate measurements.
Further Reading:
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"How To Read A Vernier Caliper" - Now you know how to physically use a vernier caliper, do a deep dive on how to read the scales.
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"What Is Metrology?" - A look at metrology as a field along with learning about other related measuring tools.
So, there we have it. Whether you're measuring using calipers in a professional setting or working on a personal project, mastering how to use a vernier caliper like a pro is an invaluable skill in precision engineering. We hope you've found this guide helpful and discovered something you didn't already know.
For all your measurement tool needs, including micrometers, calipers and other precision measuring instruments, Accu is here to support your endeavours with high-quality products and expert guidance.
Explore Our Range of Precision Measuring Tools
FAQs
Q: How do you read a vernier caliper for beginners?
A: Reading a vernier caliper can seem challenging at first, but with a bit of practice, it becomes intuitive. For beginners looking to master this skill, we recommend checking out our detailed guide on How to Read a Vernier Caliper. This article breaks down the process step by step, complete with illustrations and tips to help you become proficient in no time.
Q: How do you use a vernier caliper step by step?
A: To use a caliper, first, ensure the caliper is clean and zeroed by closing the jaws and checking the zero reading. Next, place the object between the appropriate jaws and gently close them until they touch the object's surfaces without applying excessive force. Ensure the object is aligned properly and the caliper is perpendicular to avoid measurement errors. Once the jaws are in the correct position, read the measurement directly from the scales or lock the jaws in place with the thumb screw if you need to record the measurement later.