The Basic Elements of AutoCAD 4 (Part 2): The Importance of Units

In the previous article on the basics of computer-aided design with AutoCAD, we looked at the various features of Autodesk AutoCAD that help in adding necessary details to communicate vital information. In the same context, another underrated aspect of information in engineering is the units.  

So, read on to find out why units are significant in engineering drawing and how you can modify them in the AutoCAD desktop application. 

 

Why Are Units of Measurement Important in Engineering? 

Any type of measurement, such as length and angle, needs both numbers as well as units to avoid misinterpretations. Without units, the numbers themselves have very little meaning.  

For example, if you were to say that a line's length is 10, one person might assume it as 10 millimeters while the other may think it is 10 meters. But when you add a unit at the end that says "10 meters", there's no scope for uncertainty, thereby reducing the likelihood of errors.  

If everyone involved in a project uses the same units, there will be no ambiguity. However, in a vast field like engineering, people from various backgrounds and disciplines come together to accomplish a single goal. Hence, the units that an Indian engineer is familiar with may not be intuitive for an engineer from the United States of America.  

Even if you choose to use a standard system of units, the chances of misinterpretation are still considerably higher as there are many standard systems. Hence, specifying the units wherever possible is of the essence, especially when communicating your design intent to the workers on the field. 

 

How to Choose the Right Units? 

Choosing the right units for your engineering drawing depends on various factors. Some of them are: 

• The tool you use to make the measurement
• The parameters of a specific equation
• The person or people you expect to receive the information

For example, choosing to represent the length of a door in feet is more appropriate than choosing to describe it in millimeters or nanometers.  

When it comes to determining the units for your design, there's no specific rule to follow. Rather, your decision largely depends on the nature of your project and the personnel involved. As a result, you will be informed of the units to use beforehand, or it is left to your best judgment if you are highly experienced. 

 

Drawing Units 

The Drawing Units feature enables you to make changes to the units of length, angle, insertion scale, and lighting as well.

To open the Drawing Units window, you can use the dynamic input feature of AutoCAD. Just type in "UNITS" in the model space and press enter to open the window.  

 

Length 

By default, the type of length would be set as "Decimal". You can change this by clicking on the TYPE drop-down menu to choose any of the following: 

• Architectural
• Decimal
• Engineering
• Fractional
• Scientific

After this step, you can also adjust the precision as required. The precision options you have are as follows: 

• 0'- 0"
• 0’ - 0 1/2"
• 0’ - 0 1/4"
• 0’ - 0 1/8"
• 0’ - 0 1/16"
• 0’ - 0 1/32"
• 0’ - 0 1/64"
• 0’ - 0 1/128”
• 0’ - 0 1/256"

 

Insertion Scale 

This allows you to change the units to scale the inserted content in AutoCAD. You have the following options in the drop-down menu: 

• Unitless
• Inches
• US Survey Feet
• Miles
• Millimeters
• Centimeters
• Meters
• Kilometers
• Micro inches
• Mils
• Yards
• Angstroms
• Nanometers
• Microns
• Decimeters
• Dekameters
• Hectometers
• Gigameters
• Astronomical
• Lightyears
• Parsecs

Therefore, depending on your drawings and clients, you can use the most convenient units. For example, if you are making a layout of a street, then it doesn't make a lot of sense to use units like inches or microns. In such cases, you would choose meters or miles. 

 

Angle 

If you have an angular element in your model space, you can set the angle type to any of the following: 

• Decimal Degrees
• Deg/Min/Sec
• Grads
• Radians
• Surveyor's Units

Then, in the precisions section, you can choose all the way up to a precision of eight decimal places! 

 

Lighting 

These are units for specifying the intensity of lighting. You have the following two option in the lighting drop-down menu: 

• International
• American

 

Unit Conversions 

In this section, you will explore how you can convert the units from one system to another in the AutoCAD desktop application.  

Suppose you have a rectangle in your model space as an object that you have drawn using the imperial units. Here's what you could do:

• First off, you can use the SCALE command. You can type it in the command bar or from the dynamic input, select the rectangle as your object, and hit enter on the keyboard.
• By entering a scale factor, you will be able to create an insertion object. Then, you summon the Drawing Units window again and change the units in the insertion scale.
• Now, if you check the units using the MEASURE tool from the UTILITIES section in the HOME tab of the application toolbar, you will notice that the units are now displayed in the metric system.

This is an efficient way to convert a system of units from imperial to metric in AutoCAD. You can use the same method to even convert angles from degrees to radians, length from millimeters to meters, and more. 

 

Conclusion 

The system of units in India is fundamentally different from those used in other countries, and using different units can lead to confusion regarding the design dimensions. Misinterpreting the design even slightly can cause significant and unnecessary errors. 

For the same reason, learning how to set up units and changing them in Autodesk AutoCAD is necessary. To eliminate any errors and maintain uniformity, you can manipulate measurement units as per your needs.  

If you liked this blog on computer-aided design with AutoCAD, be sure to check out more interesting and fruitful engineering design courses only on Skill-Lync. 

 

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