# How to Use Calipers

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## Introduction: How to Use Calipers

A caliper is a device that is used to precisely measure the size of different objects and is commonly used in 3D design and fabrication. It can help you measure an objects length, width and height. While you could do this with a ruler, what sets a caliper apart is that it is really good at measuring dimensions a ruler struggles with, such as round objects like a ball or light bulb. It also has the ability to accurately measure an object’s inner openings with precision such as the inside of a drinking glass.

Calipers are really good for measuring an object’s dimensions such that you could reproduce it in 3D modeling software such as Tinkercad. You may want to do this in order to make a model of something you own in order to design a custom adapter. Another use case is to use it in 3D modeling a scene. Or simply, you may just want to practice your 3D modeling skills by recreating something in 3D.

In this project we will use the calipers found in the Autodesk Innovator Kits for Classrooms.

## Step 1: The Parts of a Caliper

A caliper consists of a few basic parts.

Large Jaws
These are used to measure the outside of an object.

Small Jaws
These are used to measure the inside of an object.

Depth Probe
This is used to measure the depth of a hole inside of an object (or similar).

Main Scale / Ruler
Like a traditional ruler, this is used to measure an object in either inches (Imperial) or millimeters (Metric).

Vernier Scale
When precise measurements are needed, this can provide very fine measurements beyond what the Main Scale is capable of by itself. Using this feature won't be covered in this basic introduction.

## Step 2: Measuring the Width of a 3D Rectangular Object

To begin, we will measure a three-dimensional rectangular object. As the name implies, a three-dimensional object has three dimensions that we will need to measure - length, width and height.

Pick one side of the object that you consider to be its length. This will be the first side we measure.

Spread apart the large jaws of the caliper and then gently close them upon the object.

You can read the length measurement by comparing the distance between on the 0 marking on the main scale and the 0 marking on the vernier scale. In this case, the box is 4-5/8" long.

## Step 3: Measuring the Other Two Dimensions

Repeat this process to measure the other two dimensions (width and height) of the box.

The dimensions of the box above are 4-5/8" long x 1-5/16" wide x 3-5/8" high.

Going Further:
What are the dimensions of the object in millimeters?

## Step 4: Measuring Outer Dimensions of a Round Object

Measuring a round object is accomplished much in the same way.

However, when measuring a ball, you really only need to measure one dimension to find its diameter as the diameter will always be the same no matter where you measure from.

## Step 5: Measuring the Dimensions of a Cylinder

To measure a cylindrical object like a can, you would need to measure two dimensions. The first would be its diameter and the second is its height. The reason for this is a cylinder’s length and width are the same value, but its height can differ.

## Step 6: Measuring Inner Dimensions

There are two ways to measure inner dimensions.

The first way to measure this is to use the inner jaws. This is best when you want to measure the length of a large opening. You can simply place the inner jaws at each edge of the opening to measure its distance.

The other way to measure the inner dimensions of an object is to use the depth probe. This is best to use when you want to measure the height of a hole. To take this measurement, you simply place the bottom of the caliper along the hole's edge and then lower the depth probe until you reach the bottom.

## Step 7: Recording Your Measurements

The easiest way to record your measurements is on paper. To keep it simple, we will be practicing with the small box we measured earlier. The idea here is to do a rough sketch of the object you are trying to measure. You don't need to be an expert artist. The most important part is that the measurements are correct and you will understand what you drew if you were to look at it later on.

In order to record the measurement we will start with 2D profile views. This is what you would see if you looked at one side of the object directly from any of its sides. There are six different profile views and these include the front, back, top, bottom, left and right. The nice thing about profile views is that even if you are not good at drawing, you can likely draw an object's two-dimensional shape.

In our notebook we will use profile drawings and dimension lines to indicate the measurements of each of the yellow box's three sides. Another thing to note is that since each profile view is two dimensional, you always need at least two different profile views to record all three dimensions.

To draw a dimension line, simply draw a straight line that is equal size to what you are measuring and put arrows on each end. You can also draw perpendicular lines from the tip of the arrows to the edge of what you are measuring to help clarify what the dimension line is a measurement of.

Another fast way to record all of the dimensions of your object on paper is to draw it using 3D perspective. When you do this, you can record all of your dimensions at once.

Going Further:
If you have never drawn in 3D before or need to further develop your skills, here are some resources to get started:

https://www.instructables.com/How-to-Draw-Perspect...

https://www.instructables.com/How-to-Draw-Perspect...

https://www.instructables.com/How-to-Draw---Basic-...

https://www.instructables.com/How-to-Make-a-Two-Po...

## Step 8: Translating to 3D Software

To translate what you have just drawn on paper to the computer, open Tinkercad and create a new 3D design and give it any title you would like. I called mine "Measured Box".

If you are working in inches, click the "Edit Grid" button on the bottom and change the Units from millimeters to inches. If you are working in millimeters, you can skip this.

Select a Box from the shapes panel and place it on the workplane.

Click on the box and select one of the corner handles to bring up the length and width dimension boxes. Enter the length and width measurements that you have taken into the appropriate boxes.

You will need to convert the measurements to decimals from a fraction (if you have not done so already). For instance, 4-5/8 inches would become 4.625 inches. I translated 5/8 to a decimal by diving 5 by 8 using a calculator.

Finally, set the height by clicking on the box again and selecting the height handle (in the center top of the box). Enter the height measurement in the dimension box.

Your virtual box should now have the same dimensions as the one you measured in real life.

To finished it up you can also change the color of the box to match the one you measured. They now should look roughly the same!

## Step 9: Put It Into Action

Now that you know how to use calipers to measure real world objects, you can put your new skills to work by designing a Straw Roller Coaster in 3D using Tinkercad!

## Step 10: Share an "I Made It"!

Post an "I Made It" below to show us a 3D object that you measured using calipers and modeled in Tinkercad!

## Recommendations

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• ### Puzzles Challenge

Very nice tutorial. My students struggle with calipers and this should help. I was particularly interested in that cute little sketchbook with the CAD terms. Is this something you made or found? I'd love to post those images and definitions as reminders in my room.

The notebooks are part of the Autodesk Innovator's Kit and something we made.

That said, here is the original poster the notebook is based on and also a Tinkercad shortcuts handout.

Could you tell me where to buy the Autodesk Innovator's kit ?
Thank you

I scanned the item for one purpose: a refresher on reading the Vernier scale. I did not realize the item was for school pupils. Maybe next time - that is where the precision comes in play.

Wow, lots of caliper/imperial hate. I thought you explained the use of calipers perfectly as an introduction. I use a pair everyday. While I like my dial calipers without a vernier scale, I like the vernier scale on my micrometer for precise measurements.

“Vernier Scale: Using this feature won't be covered in this basic introduction.”
Not sure why you skipped this important part, which is a key thing to learn. It’s easy to explain and would make your document even better.

This is an introduction intended for students in the 5th and 6th grades. I decided that explaining how to calculate a dimension to a fraction of a mm was not pertinent to this introductory lesson and is not necessary for understanding the fundamental operating principle of a caliper. I will cover it in future Instructables where I will go over more advanced topics.

For the next version, I want to suggest, you add the 4th way for
measuring with calipers to the 3 (outside, inside, depth gauge) you
already presented: I call it "shoulder".
The fixed and moving part of a caliper when closed completely are even on top. So when you open the caliper, you get a shoulder which you can use for measuring like in the image.
(Yes, another crappy plastic caliper, but good enough for measuring magnets :-)

And, yes, I also prefer SI units :-)

Cheers!

That's a great tip! Thanks for sharing. Perhaps I will add it in!

I've worked in drafting offices for over 40 years, and used calipers, verniers, analog dial and digital. Not to mention about 6 different brands of professional CAD software. Anyone doing serious work would not use a cheap plastic vernier like the one shown. You did not fully explain how to read it neither in metric (SI) nor in inches. In the tennis ball photo it looks like 2-1/2 or 2.50 inches plus 1/128". So that would be 2.5078125" On the metric scale it looks like 63 mm plus 10 X 0.05 = 63.5 mm. Dividing by 25.4 = 2.50". Better to invest in a battery powered digital.

These instructions are intended for 5th and 6th graders who are first getting started on their design journeys. I didn't want to overwhelm them by introducing the Vernier scale. It will be covered in future Instructables.

Sir. You write:
”In the tennis ball photo it looks like 2-1/2 or 2.50 inches plus 1/128"
So, what do You do here is that You divide a inch 1/128 plus it to what WHY?
Where does that 1/128” come from?

Actually, the tool is poorly made. I have a very similar one except the inch scale is on top edge and millimetres on lower edge. The little vernier inch scale says 0...4...8 and followed by [1/128 in.] which means that one can count up to 8/128" = 1/16, because your inch scale is in 1/16' divisions. Now looking at the photo, the first mark after the 0 lines up with the 9/16" mark on the main scale, so we should add 1/128". So assuming the scale is accurate (probably isn't) we would read 2-65/128 inches, or in decimals = 2,5078125".
On the millimetre scale, the 10 on that vernier [0.1.2.3.4.5.6.7.8.9.10] lines up with the 102 mm mark on the main scale, we add 10x0.05 = .0.5, so the measurement is 63.5 mm. It is kind of confusing because there are divisions of 0.025 mm between the numbered 0.05 mm divisions. Those plastic calipers are OK for rough work, and might even be used if one wants to get a quick conversion. In other words, if you set it to 5", it will read 127 mm, and 127/5 = 25.4. exactly. And if the caliper was really accurate, we could say that the metric scale is more precise, because 0.025 mm is about 0.001" while the 1/128" is about 0.008".

Yeah, I 2nd the support for metric. Imperial is only good if you're going to Home Depot or something. All serious design is done in metric nowadays.
Once you get into using the Vernier scale, it only makes sense to use it in metric.

You'r ible is really needed for, say, youngsters (you know, them young people), fair enough, BUT, really: Go with SI-system, that is: in this case in millimeters..
Reason to why to do this: The US. Imperial with them inches, if not yet but in close future, will be using the SI-system even for you ower there behind the pond.
Did you know that them astronautical- and astronomical- (Nasa included), +++ many others
have used the SI eversince the -50's ? Why? (humor) e.g. the distanance to the moon could be something like 45,8444,254,255,003 5/8 of an inch (count that), ok, you could translate it to feet, and then to yards and then to miles.... Geee I'll give up :)
FOR GODS SAKE go ower to SI-system
Cheers
ps. plz. don't get affended

I really like the details in this instructable. By any chance, do you have a version for reading mm. I prefer to have my students design in mm.

Not currently. I decided to go with inches for this first round, but your feedback is noted.