The Vernier Caliper is a precision tool that can be used for measuring internal as well as external ranges/intervals with exceptionally high accuracy. The measured results are interpreted from the tool’s scale by the operator. Dealing with a Vernier and interpreting its readings is rather difficult compared to using a Digital Caliper, its advanced version, which comes with an LCD digital display where all the readings are shown. As for the manual type of the tool – both imperial as well as metric scales are included.
Vernier Calipers are operated manually and still available to be purchased and remain popular because of being cheaper in comparison to the digital variant. On top of that, the digital variant needs a small battery while its manual counterpart does not require any power source. Nevertheless, a digital caliper provides a wider range of measurements.
What is a Vernier Caliper?
A vernier caliper is a measuring device used to precisely measure linear dimensions. In other words, it measures a straight line between two points.
However, it is also a very useful tool to use when measuring the diameter of a round objects like cylinders because the measuring jaws can be secured on either side of the circumference.
Vernier calipers are super useful and a great tool to have in the tool box.
Why use Vernier Calipers?
Vernier calipers have both a fixed main scale and a moving vernier scale. The main scale is graduated in either millimetres or tenths of an inch. The vernier scale allows much more precise readings to be taken (usually to the nearest 0.02mm or 0.001 inch) in comparison to a standard ruler (which only measures to the nearest 1mm or 0.25 inch).
Vernier calipers have both a fixed main scale and a moving vernier scale.
The main scale is graduated in either millimetres or tenths of an inch.
The vernier scale allows much more precise readings to be taken (usually to the nearest 0.02mm or 0.001 inch) in comparison to a standard ruler (which only measures to the nearest 1mm or 0.25 inch).
Parts of a Caliper
Vernier, dial and digital calipers consist of similar parts. The only difference is the measurement reader. Here are the main parts of a caliper:
Internal/Upper jaws: Used for taking inside measurements such as the diameter of a hole or slot.
External/ Lower jaws: Used for measuring outside dimensions such as width, length and diameter.
Depth rod: A small rod that protrudes when the thumbscrew is turned. The rod is used for measuring the depth of holes.
Step gauge: Measures the distance from an edge to another point on an object.
Scale: Runs along the beam of the caliper. This gives you the measurement reading.
Thumbscrew: Adjusts the measuring faces of the caliper (the jaws and the depth rod).
Lock screw: Secures the jaws into place so the object is removed without moving the caliper’s jaws.
How to Use a Vernier Caliper: 4 Steps
A Vernier caliper is an instrument that measures internal or external dimensions and distances. It allows you to take more precise measurements than you could with regular rulers.
1. Slide one of the jaws against the object. The caliper has two types of jaws. The larger ones tighten around an object, to measure the distance across it. The smaller jaws fit into an opening, and can then be pushed outward to measure its internal diameter. You can adjust either pair of jaws by sliding the smaller scale. Once you’ve got one of the jaws in position, tighten the locking screw if there is one.
2. Read the main scale where it lines up with the sliding scale’s zero. The main scale on a Vernier caliper typically tells you the whole number plus the first decimal. Read this just as you would a ruler, measuring to the zero mark on the sliding (Vernier) scale.
- For example, if the 0 on the sliding scale lines up with the 2 inch mark, your measurement is 2 inches. If it lines up past 2 inches by six tenth-inch marks, your measurement is 2.6 inches.
- If the result is between two lines, just use the smaller value. Do not try to estimate a value between the two lines.
3. Read the Vernier scale. Find the first mark on the Vernier scale that lines up perfectly with any line on the main scale. That mark tells you the value of the additional digits.
- For example, the 14 on the Vernier scale aligns with a line on the main scale. Let’s say the scale represents 0.01 inch increments, so the 14 represents 0.014″.
- It makes no difference which line on the main scale it aligns with. We’ve already taken our reading from the main scale; don’t take another one.
4. Add the numbers together. Add the main scale and Vernier scale results together to get the final answer. Make sure you use the correct units as labeled on each scale, or you won’t get the right answer.
- In our example, we measured 2.6 inches on the main scale, and 0.014 inches on the Vernier scale. Our final measurement is 2.614 inches.
- The digits don’t always line up this neatly. For example, if the main centimeter scale reads 0.85, and the Vernier 0.01 cm scale reads 12, adding them together results in 0.85 + 0.012 = 0.862 cm.
How to Read Vernier Calipers
Reading the measurement on a Vernier caliper can be tricky. However, it can measure to the accuracy of one-thousandth of an inch (up to 2 decimal places). A Vernier caliper has two rulers: the main scale and the sliding Vernier scale. Reading the caliper is a two-step process:
The main scale contributes to the main number and one decimal place. On an inch Vernier caliper, each increment on the main scale represents one-tenth (.1) of an inch. Each division in-between each tenth of an inch represents twenty-five thousandths (0.025) of an inch.
The Vernier scale is located on the sliding jaw and typically has 25 graduations. The scale contributes to the second decimal place in the reading and represents a thousandth of an inch (0.001), with each .005 inch numbered successively as 0, 5, 10, 15, 20, and 25.
To read a Vernier caliper:
When you measure an object with a Vernier caliper, the Vernier scale will slide to the right.
Read the large number division first from the main scale to the left of the “zero” of the Vernier scale.
Find the largest whole inch mark to the left side of this index line.
Still using the end of the zero mark on the Vernier scale as the index line, find the largest .100-inch mark to the left side of this index line.
Now, look at the Vernier scale.
Note how the lines on the Vernier scale match up with the lines on the main scale. The way that the scale is made, only one of these lines will match up correctly.
Still using the end of the zero mark on the Vernier scale as the index line, record the whole number of .025-inch increments to the left of the index line.
The final reading is the sum of these two readings.
A Vernier caliper is one of the most precise measuring tools. It is preferred by most professional and experienced woodworkers for its precision and efficiency in providing correct measurements. Learning how to use a caliper is important for any woodworker to be able to create precise and perfect projects at all times.
Aside from measuring with a Vernier caliper, care and maintenance of this measuring tool is a must. A caliper could accumulate dirt and grime after using it on different objects and therefore it has to be cleaned carefully before it is stored away. Finally, there are traditional calipers and there are digital calipers. Learning how to use a traditional caliper is necessary before moving to a digital device to understand the concepts behind the use of a caliper in making precise measurements.