AUTOCAD LESSON - 10

SECTIONAL VIEWS :

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Putting your skills to use with Section Views.

In drafting there are a lot times where you want to give a lot of information, but not all of the views are helping to get your message across. Sometimes you just need to slice the object(s) down the middle and show what the guts look like. Using this method, you get a cross section of the part, or a "Section View".

Take a look at the drawing above. You'll see a complex assembly drawing and two different section views. On the far left, you see the line that indicates where Section B-B is. On the right side, you see the section view. Does it make sense to you? What you are seeing is the cross section view of the metal beam part of the of the bracket. It's shown so that you can see what size the area is without having to look at the entire side view of the assembly. Section views are used for clarity.

Look for the indicators for Section A-A. Then look at the top right view. You'll see that the beam part is shown as well as the hole that is drilled through it.

Section views are used in Mechanical and Architechural drafting. Anytime you need to show some detail that isn't readily seen from an exterior view, "cut it up" and draw it.

Looking at Section Views

If you understand Orthographic Projection and Hatching (you read the other two tutorials, right?) then you should be able to handle section views easily. Have a look at the image below and see if it all makes sense.

What you see is a very simple block with a hole drilled. This shows that the section view and the front view are almost the same. In fact, I just copied the Front view down to begin the section view. I changed some linetypes and then hatched it.

If you have more than one part in your view, you will need to make sure that it stands out. Here I have the same part as above, but with another piece placed inside it.

Here's an example of how a section view can be used in Architechural drafting. By using standard hatch patterns, someone else can look at the drawing and see that this shows a concrete foundation with earth on one side.

I think by now you're getting the idea of how section views and hatching help to tell the story of what you are drawing.

Drawing Section views in AutoCAD

For this exercise, we'll start with a simple drawing. Begin by drawing the part below, and as you're drawing, think about what the section view will look like. You do not need to draw the Isometric view, it is just for reference.

To draw the "Cutting Plane" that marks the section, draw a line and then use the leader command to make the arrows. Add text for the "A"s. Ok - what is your section view going to look like?

The Cutting Plane points up from the front view, It doesn't mean that it's pointing at the top view, but in this case it works. Also note the the Cutting Plane is in the middle. So if you chose the Top View, you're correct.

Copy the Top View. Straight up will work fine. You can keep the dimensions. It's a good idea to make sure that it is directly above the other view in case you have to stretch part of it. Then you can do both views at once.

What lines need to be changed? Do you still need hidden lines?

This is what your Section view should look like before hatching:

Is it still making sense? You needed to trim the line where the shaft on the right joins the part, because in the section view, this is solid. You needed to change the lines for the two holes from hidden to solid because they are not hidden any more. You should now be ready to add a Hatch patten to the view.

The Hatch command might be a little different depending upon the version that you are using. This example shows AutoCAD 2012.

Start the Hatch command and pick in the spots shown below. You want all three areas picked at the same time so that the hatch creates one object instead of three. This is needed so that you can edit the hatch and all the areas will look the same.

The areas picked will fill up with the last used hatch pattern and settings that were used. That's fine, we'll edit them now.

This is a big toobar / ribbon for this command. There are really only three items you need to be aware of to make it work:

• Pattern: The pattern should indicate what material is used in the area that is hatched.
• Angle: Most of the time this will be 0 degrees, but sometimes you want to change it.
• Scale: This is the one that gets changed a lot. If your hatch pattern 'looks solid' - then you usually have to increase the scale because the lines are too close together. If the hatch pattern 'looks empty' - then you might have to scale it down because the lines are too far apart. The scale will vary depending upon what size your drawing is.

If everything went well, the Section view you have should look like this:

It's up to you if you want to put your hatch on a separate layer. It can help a lot as you get into more complex drawings. As you learn about printing through Layout Tabs, think about how having your Hatch can be useful on it's own layer - and maybe more than one layer.

Other uses for Section Views

Here is a section view that is used to show a break in a solid bar and a pipe. This is a common way of showing long pipes that don't fit in your drawing, just add a break, but dimention the full length.

Here's an exercise for you: reproduce the image of a foundation below:

More exercises from Textbook of Machine Drawing. Draw these parts out in Orthographic View and then draw the Section view.

Conclusion

Section views are not usually very difficult to draw, because you should have a lot of the information first. You will draw your sections last and try to base them off of existing drawings first.

If you have the opportunity, look at drawing sets and see where they are used. If you are drawing something try out a section view, it's good practice for Hatching and also for developing your "CAD" eye.

Here's a video that shows helps explain the Section view drawing technique.

AUTOCAD LESSON - 9

ORTHOGRAPHIC PROJECTION :

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Putting your skills to use.

So far in this level you have been learning the basic 2D AutoCAD commands. What you learned in this level will be a very large part of what you use in your daily drafting. This tutorial isn't going to teach commands, but will instead show a common technique that is used a lot in 'Mechanical" drafting. It will also ask you to think about what you are drawing, and how it needs to be represented.

Mechanical drafting is a field within the drafting world. In simple terms, it is used to describe the methods for drafting and designing machines, assemblies and in a nut shell, the 'parts' that used in everything from a fork to a Formula 1 race car. It doesn't include anything that involves buildings and structures (Architectural & Structural drafting) or landscapes and roads (Civil drafting and engineering).

Now just because you are dreaming of becoming an Architect, it doesn't mean that you should skip this tutorial. In fact, you will likely need to use these concepts or read diagrams related to this subject. So read on!

What is Orthographic Projection?

If you look at the image below, you will see a drawing for a part. It shows the object with a top view, a front view and a side view. You'll also see an Isometric view that is sometimes used to give a more visual look. This tutorial won't cover Isometric drafting as it is shown in Tutorial 3-2. Save your drawings that you do in this exercise for more practice in that lesson.

The reason that this method is used is that you can take a designed part, draw it, dimension it and then give all the needed information to the manufacturer.

In some cases only 2 views are needed, but for anything more than a simple part, 3 or more views are needed. Very complex parts will need 6 or more.

There are 2 methods of deciding what views are used and where they are placed in the drawing. I'll borrow some info from Wikipedia to show this:

First-angle projection (European Standards) In first-angle projection, the object is conceptually located in quadrant I, i.e. it floats above and before the viewing planes, the planes are opaque, and each view is pushed through the object onto the plane furthest from it. (Mnemonic: an "actor on a stage".) Extending to the 6-sided box, each view of the object is projected in the direction (sense) of sight of the object, onto the (opaque) interior walls of the box; that is, each view of the object is drawn on the opposite side of the box. A two-dimensional representation of the object is then created by "unfolding" the box, to view all of the interior walls. This produces two plans and four elevations. A simpler way to visualize this is to place the object on top of an upside-down bowl. Sliding the object down the right edge of the bowl reveals the right side view. Image of object in box, with views of object projected in the direction of sight onto walls using first-angle projection. Similar image showing the box unfolding from around the object. Image showing orthographic views located relative to each other in accordance with first-angle projection. Third-angle projection (USA Standards) In third-angle projection, the object is conceptually located in quadrant III, i.e. it lurks below and behind the viewing planes, the planes are transparent, and each view is pulled onto the plane closest to it. (Mnemonic: a "shark in a tank", esp. that is sunken into the floor.) Using the 6-sided viewing box, each view of the object is projected opposite to the direction (sense) of sight, onto the (transparent) exterior walls of the box; that is, each view of the object is drawn on the same side of the box. The box is then unfolded to view all of its exterior walls. A simpler way to visualize this is to place the object in the bottom of a bowl. Sliding the object up the right edge of the bowl reveals the right side view. Here is the construction of third angle projections of the same object as above. Note that the individual views are the same, just arranged differently. Image of object in box, with views of object projected in the direction of sight onto walls using first-angle projection. Similar image showing the box unfolding from around the object. Image showing orthographic views located relative to each other in accordance with third-angle projection.

 

Ok - that was some fun theory - thank for reading it. One last bit of info before we get back to CAD stuff. Since there are 2 kinds of standards, how do you know which is which when you have a drawing in front of you? There is a standard symbol that is used in the title block to indicate which method was used.

This symbol shows a simple cone and displays the projection. Think about which symbol represents which method, then move your mouse over the images to see if you were correct.

Because I am in North America and was trained to use the "Third Angle Projection" method, that is what I will show in this tutorial. The techniques for drawing are the same, it's just a matter of which direction you 'project' or draw the lines.

Here's a short video for you that explains these concept visually.

Drawing 3 View Orthographic Projection

For these exercises, we'll start by looking at an Isometric drawing of an object and then draw the Front, Side and Top views using the dimensions we're given. In the workplace, you might find that you are given a part to measure and then draw, or you might be designing the part yourself.

Here's the part that we'll draw in this tutorial:

This is a very simple example to get you used to the concepts. You'll have more practice exercises at the bottom.

Ok, the first question that you'll ask yourself, is "Where do I start?". I recommend that you start where you have the most information. This will sometimes be the front or the top - it depends upon each drawing. In this case, I will start with the front and draw it.

You don't need to worry about dimensioning it at this point - wait until you have all of your views drawn. Ok, this should have been easy enough, so now you can start drawing the top view.

To draw the top, you need to 'project' the lines up. Draw lines up from the main points in your front view. Make sure you have your Osnaps on (include "Quadrant").

Now that you have the vertical lines, draw the horizontal lines. Make sure you leave enough room to draw the width (via OFFSET) and space between the views.

Now you almost have 2 views drawn. Trim the lines so that you are left with just the lines you need.

Stop and check to make sure that you didn't forget any lines. It's very easy to miss some.

Now it's time to jump ahead a little and take a side trip. Read Tutorials 4-3 to learn about Linetypes, because you will need them here. After reading the tutorial, return to your drawing and load the Hidden and Center linetypes. These are needed to add more information in your drawing.

If all went well, you should be able to load the linetypes and scale them (LTS with a value of 10 or 12) to fit with your drawing.

What you see above is the completed Top and Front views. Do you understand why there are "Hidden" lines? They are there to indicate that the hole (circle) is drilled right through the block. Where would the lines be in the hole was only drilled half way through? The center lines are used to show the the hole and the arc have the same center point. These are both common and standard CAD methods and you need to understand them.

One more view to draw. This will be the side/right view. Can you picture it yet?

To get started on the side view, you have to establish where it will be placed in the drawing. In this example and using the 3rd Angle projection, it will be shown to the right of the front view. For exact placement, you need to draw more projection lines.

What you see in the image above is that I established the top right corner of my front view by projecting 2 lines. Then I drew a 45 degree line up from the corner.

Now I can start projecting lines from my top view to create the side view. The line that is indicated by the 'Project Down' leader will be the left side of my Right Side View. I would project another from the other side of the top view and that would establish the width of the right side. Also note that by using this technique the top and side views are the same distance from the front view.

From there I just need to project to the right from my front view.

Almost there. Now you just need to trim up some lines and change the linetype for the hidden lines. Final goal is to draw this:

Once you have all of your lines, your center lines and your hidden lines, you are ready to dimension and add any notes that are needed.

Think about what commands you used in this tutorial. You used LINE, CIRCLE, OFFSET & TRIM. You also use Layers and then learned about Linetypes. What this shows is that you don't need to use a lot of commands, but it's your knowledge of how those commands works that makes your reputation as a CAD user.

Extra Practice: Draw the missing Right Side View and the other views (except Isometric) for this drawing.

Extra Practice: Here is a scan from an old (1919) drafting book that I found on Google Books. This image has 4 separate exercise to keep you busy. Draw what you are given, and then draw the missing view.

Extra Practice: Draw the 3 views needed for each of these blocks. Extra 1 - Extra 2

Just one more thing I should mention. This method of drafting can be used in other ways as well. To the right is a simple piece of duct work drawn in AutoCAD. It's a straight piece that has been cut at an angle so that it can be connected to another piece to form a bend. Drawing in 3D isn't very hard when you know how. But if I sent this to the manufacturer, he wouldn't really know where to start. So I would have to send him a drawing of the tube rolled out. This would give him a template to cut the shape and manufacture the part. Think about what this shape would look like if it was flat. How would you draw it? How would get the curve correct? Do you think that this sounds like a job for Orthographic Projection? Yes it does. The drawing below shows how this could be drawn to show all aspects of this part. I have the diameter of the pipe and the length to the top and the length to the bottom. Since I have the diameter, I also have the circumference. The circumference tells me the length of material that will be needed to make the piece. The part is drawn in Magenta, and the projection lines are in Blue. What I needed to do was use the DIVIDE command to divide both the circle and the line that represents the circumference. Then it was a matter of projecting down and to the right from the circle, and up from the circumference line. This gave me a grid to use for the SPLINE to create the curve. The Auxiliary view was drawn with a few projection lines and anELLIPSE. Try this if you like and follow the command line for the commands you don't know. This might be tough, but take your time.

Here's a video that shows how to construct a basic Orthographic Projection drawing.

AUTOCAD LESSON - 8

DIRECT DISTANCE ENTRY AND OBJECT TRACKING :

Direct Distance Entry

As mentioned earlier in the lessons, there are many ways to do things in AutoCAD. To enter distances, you have been shown Absolute, Relative and Polar Coordinates. I've spent the previous 8 lessons showing you foolproof ways to enter data (the hard way). Now you will be shown four more ways to tell AutoCAD where the locate the point you are drawing to (the easy way).

DO NOT FORGET THE BASICS OF MANUAL ENTRY

Direct Distance Entry (or DDE) is a way of bypassing the usual ways of entering in coordinates. and just entering the distance.

The method is quite easy.

Make sure that you have set Ortho (locking your input to vertical and horizontal) by pressing the F8 button and checking to see that the "Ortho" button is depressed (blue) on the status bar like this: 
Your F8 key will toggle Ortho on and off.

Lets say you want to draw a line from one point directly to the right 10 units.

Start the Line command and click on the screen anywhere, then more your cursor to the right of that point. If Ortho is turned on, the line should only point directly to the right and not at an angle. Now type in 10 <ENTER>. Press <ENTER> again to exit the command. You now have line that is 10 units long.

That is a very easy way to draw line segments. If Ortho is not set, your drawing will get messed up very quickly and will not be easy to fix. I have seen too many students take this easy route and destroy their projects, fail the class and become homeless. So don't do this.

Polar Tracking

Now wouldn't it be cool to draw angled lines (like the short ones in the above image)? Well you can, but first you have to make change in your settings.

Type in DSETTINGS and you get the Drafting Settings dialog box, go to the "Polar Tracking" tab. :

Then make sure that Polar Tracking is On  (press your F10 key to toggle it on and off) and then select the increment angle.  I recommend using polar settings with 45° increments unless you specifically need something else.

In the example above, I made 4 lines 1 unit long using Direct Distance Entry (DDE). See if you can duplicate this on the left end of the 10 unit line you just drew. The process is the same as you did for the DDE of the previous line. Make sure your increment angle is 30° and draw a line 1 unit long using DDE..

You can not have Ortho and Polar Tracking on at the same time. As you start to draw more, you will see that these two features are great time savers. There will be times, though, when you have to use absolute and relative coordinate entry (especially in 3D).

Refer back to the assignment in Lesson 1-2 and draw using the methods shown in this lesson.

Now I'm going to repeat this one last time:

Make sure you have either Ortho or Polar tracking on and don't forget how to manually enter points!

 View the video for a sample of DDE.

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Object Snap Tracking

Now you've just seen how you can find distances from points and measure accurately, but what if you want to find specific points based on previously drawn objects? You can use Osnaps, but they don't always find the point you need.

Consider that you want to draw a circle in the middle of a rectangle like the example below:

In the olden days, you would have drawn a line from opposite corners of the rectangle to find the middle, then snapped to the midpoint of that line for the circle's center point, drawn the circle and then erased the reference line.

Now you can use object snap tracking. This is a way of finding reference points and drawing from them. To do this exercise, make sure that your Midpoint Osnap is on.

Draw a RECTANGLE from 0,0 to 4,3

Make sure that the Object Snap Tracking and Osnap button are depressed. 

Start the CIRCLE command.

Move your cursor over the midpoint of the bottom line of the rectangle. You should see a light dotted line project vertically through your cursor. Now more your cursor to the midpoint of the right vertical line of the rectangle. As you move your cursor towards the center of the rectangle, you should see the 2 dotted lines cross. It should look like this:

Once you see both lines, you can pick and the center point will be exact center of the rectangle. Give your circle a radius of 1".

This is a very simple example, but as you start drawing more complex shapes, this will be a handy to tool to master, and a great time saver. Object tracking will work with any Osnap that is invoked. But always check to make sure that you are picking the point you want.

Now the fun begins! You can combine Object Snap Tracking with Direct Distance Entry. What if you want to draw a line that starts 10 units above the top right corner of a rectangle? You can just use these techniques in tandem to move up from the corner and and type in10 to get the starting point.

This technique is a great time saver. In older versions, you have needed to offset the rectangle, draw the line and then erase the rectangle. Try this out on your own.

 View the video to see object tracking in action.

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Dynamic Input

Now it's time to put all these concepts together and combine them with on-screen help that's called 'Dynamic Input'. In older versions of AutoCAD, users relied solely on the command for information. Later versions of AutoCAD added Dynamic Input to put a user's keystrokes in the drawing area near their cursor.

Turn on Dynamic Input by clicking on the status bar (toggle with F12): 

Now when you draw, you will see all kinds of information on the screen.

In this example, I have drawn a line starting at the midpoint of the bottom line going up 20.5 units (which I manually entered) at 135°. Once I enter the distance, I can press the Tab key to switch over to the Degrees and enter a value there. I could also have typed@20.5<135 using relative coordinates. By default you are in the first field (length) - press the TAB button on your keyboard to be able to enter the angle.

If you are new to AutoCAD, I recommend turning this feature off as it takes your eyes off the command line (which will prompt you for information).

To review, AutoCAD provides some nice tools to enhance your productivity. Use them, master them, but don't forget the basic of inputting points. Especially when you do 3D work, manual entry becomes valuable.

 View the video to see how Dynamic Input works.

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Extra Practice: Try drawing the extra exercises again using these methods. Find out which one works best for you, and when to use the different techniques in various situations. See if you like using Dynamic Input, or if you prefer to have it off. If you can draw all these exercises quickly (about 1-2 minutes) you have learned the lessons and should move on to the next lesson. 

AUTOCAD LESSON - 7

 LAYERS / DIMENSIONING / TEXT / SCALE WITH ASSIGNMENTS:

Now that you've learned a lot of the drawing and modifying commands, it's time to go to the next level. This lesson will introduce you to text, dimensioning and the concept of layers. Without dimensions you can not communicate what size your objects are. Is it a real house or a doll house? Text is used to convey information that is needed other than size - materials, manufacturing process, part numbers, etc.

What you will do is take one of your previous assignments, save it to a new name and then add text and dimensions to it. These are the commands you'll be learning.

Command	Keystroke	Icon	Location	Result
Layer	Layer / LA		Home > Layers	Starts the Layer and Linetype property dialog box
Text	Text		Home > Annotate > Single Line Text	Creates a single line of text
Dimension	Dim	Many	Home > Annotate >Dimension > (pick one)	Dimensions previously drawn objects
Scale	Scale / SC		Home > Modify > Scale	Proportionately resizes (or scales) objects

Begin by opening up Assignment #5 from your CAD folder.

Using the SAVE AS  option, immediately save it under the name Assign6.dwg

Click HERE for the GIF version of the file.
Click HERE for the DWG version.

The first thing you want to do is create three layers. Layers are used to organize drawings. Imagine a large project for a high-rise tower. The designers would create layers for the electrical, plumbing, landscape and more. It is necessary to control the drawing and turn some layers off and view only the ones you want. This is one reason why layers are needed. When you go on to use AutoCAD professionally, every drawing you deal with will have layers.

You will be creating a layer for the dimensions, one for the objects (lines that were drawn) and another for the text. Start the LAYERcommand (LA). This will bring up the Layer Properties Manager Palette (shown below). We'll cover the things that are used in this lesson.

Looking at the Dialog Box, you will see a lot of information.

From left to right, this is what the columns are for (not everything is used in this level).

Status	This column has a green check to indicate the current layer (all new objects will be drawn on that layer). Double click here to make the layer current.
Name	Give the layer a good, descriptive name (but not too long)
On	Turns the visibility of that layer on (visible) or off (invisible)
Freeze	Similar to 'On', but can be used in Viewports (later tutorial)
Lock	Retain visibility, but disable modifying objects on the locked layer.
Color	Used to select the color for objects drawn on each layer
Linetype	Used to select the linetype for objects drawn on each layer
Lineweight	Used to select the lineweight for objects drawn on each layer
Plot Style	Plot styles are used to define how objects are plotted - this can be different from the properties described above.
Plot	Set the layer to either plot (on) or not (off)
New VP Freeze	When on, it will freeze the selected layer in new viewports when they (viewports) are created
Description	Use this to give a description to your layer system - very important when working with other users.

Now you have the dialog box on your screen, click the 'New' button . This will create a new layer and give you an opportunity to name it. Name this layer TEXT. Click on the small box towards the right and select yellow for the color. Create another layer and call this oneDIMS (for dimensions), and make its color red. Finally, create a third layer and call it OBJECT and make its color green. You have just created three new layers in your drawing. Highlight the TEXT layer and then press the 'Make Current' button . This makes the TEXT layer current and anything you draw will be placed on that layer. Your Dialog box should look like the one above. If it does, press OK to close the dialog box.

Now that you have your layers, select all your objects and then look for the layer tool panel. There is a droplist there with all of your layer names. With your objects selected, change the layer to OBJECT. If all went well, your lines and circles will now be green and on the object layer.

ADDING TEXT

A later tutorial will discuss text in more detail, but for now see what is involved in adding text. TEXT is your current drawing layer now, so what you will be doing is creating some text now. Type in TEXT on the command line. Look at the command line.

Command: TEXT
Justify/Style/<Start point>:

The first thing AutoCAD wants is a starting point for the text. Type: 0,0 to place it at the bottom left corner of your drawing. Notice that there are other options you could make, but ignore them for now.

Height <0.2000>: <ENTER>

Next, AutoCAD wants to know how tall you want your letters to be. For this assignment, you want them to be 1/4" tall. Type in .25 at the Height prompt.

Rotation angle <0>: <ENTER>

One more thing before you start typing in text, tell AutoCAD if you want to have your text rotated. Not this time, so press <ENTER> to accept the default of 0 degrees.

Text: (YOUR NAME - ASSIGNMENT #6)

Finally you can type in what you want to put on the drawing. At the prompt, type your NAME and ASSIGNMENT #6  then press<ENTER>.

You will see that AutoCAD has placed your name in the bottom left corner at 1/4" high and in yellow on the 'Text' layer.

You don't really want your name jammed into the corner like that so move it up and over 1/8" (Remember your MOVE command and relative points : @.125,.125)

Now it's time to start dimensioning your drawing. Bring up the Layer dialog box and make DIM your current layer.

This is one time when I recommend to use the icons. Dimensioning is A LOT easier this way. If you don't see your dimensioning toolbar on the screen, right click on one of your toolbar icons and check the Dimension checkbox. You'll see the toolbar appear. Close the Toolbars dialog box.

There are several different types of dimensions, here are the ones you'll be using in this lesson (Each of the dimensioning icons gives you a quick clue as to which type of dimension it will create.) The image below shows you the standard dimensioning icons. This list below shows you which dimension types are available on the Dimension tool panel.

Here are the ones you'll be using in this lesson.

Linear dimensions are used for dimensioning either horizontal or vertical distances.

Aligned dimensions will measure the actual length of an angled line.

Radius dimensions will give you the radius of either arcs or circles.

Diameter dimensions are used on circles.

Angular dimensions will measure the angle between two lines that you pick.

Baseline dimensions are a special type that will automatically stack dimensions along one plane as you pick points.

Once you have your objects drawn, you need to go to the menu at the top of the screen and click on Annotate. This will show the Dimension tool panel as well as the text panel and others.

The type of dimension you pick will depend entirely upon what information you want to convey to the person reading the drawing. Look at the sample drawing and pick out the different types of dimensions and where they are used.

We'll start with the most common (and easiest): Linear Dimensions. You'll use this type to add dimensions to the rectangle in the bottom left of your drawing. Pick on the icon and then look at the command line.

Command: _dimlinear
Specify first extension line origin or <select object>:

It asks for either the origin of the first dimension line (a starting point) or you can press <ENTER> to select a particular line. Turn yourOSNAPS on to endpoint only. Pick the top left corner of the rectangle. AutoCAD then asks for the second extension line origin. Pick the top right corner. You'll then see the dimension appear and AutoCAD asks for the Dimension line location. Pick somewhere just above the line where you think it fits well.

AutoCAD then shows you the length that it found to be the length of the line you just dimensioned. The following lines show what you should have seen on your command line:

Specify second extension line origin:<SELECT TOP RIGHT CORNER>
Specify dimension line location or
[Mtext/Text/Angle/Horizontal/Vertical/Rotated]:<PICK ABOVE THE LINE>
Dimension text = 3.000

Now dimension the line on the left side using the same method.

Now you want to dimension the radius of the fillet on the object above the first box. Pick the icon for radius dimension. AutoCAD asks you to select an arc or circle. Pick the arc on the top left corner. Again AutoCAD then wants you to pick the dimension line location. Pick anywhere outside the arc where the dimension fits well.

Looking at the top left object on the sample sheet, notice that there are a few ways to dimension the corners. Start on the bottom left. Pick the Linear Dimension icon. Instead of picking the two endpoints, press <ENTER> and AutoCAD will ask you to select the object you want to dimension. Pick on the angled line in the bottom left corner. As you move your cursor around, you'll see that you could place it either to the left or below the line. Choose one or the other and place your dimension. Repeat these steps to add the other dimension.

At the top left, you want to add an Aligned dimension. Pick the icon for this. As with the linear dimensions, you can either pick the endpoints or press <ENTER> to choose and object. When you're asked to place the dimension, you'll see that you can only move parallel to the line that you picked. Place the dimension line somewhere outside the object.

Now you're going to dimension the angle on the bottom right corner of the top box. Pick the Angular dimension icon. Pick the bottom line and then the angled line in the bottom right corner. Place the dimension so that it looks like the one in the sample.

Now its time to dimension the circle. Pick the icon for the Diameter dimension. AutoCAD then wants you to select the arc or circle. Pick anywhere on the circle. Then you have to place the dimension line somewhere. Pick a good spot for it.

Dimension the 1" line in the circle as shown using a linear dimension.

Dimension the top left box of the array as shown using Linear dimensions.

Dimension the space (0.75) between the two rows by picking the endpoints of the lines.

Dimension the space (0.75) between the columns as shown.

Now for the tricky part. You want to add baseline dimensions to the column distance dimension you just created. Pick the icon for the baseline dimensions. Look at the command line:

You may be asked to select the base dimension. If so, pick on the 0.75 dimension for the column. Then you're asked to Specify a second extension line origin. Pick where P1 shows you on the sample drawing. AutoCAD then will get you to keep repeating this process until you press <ENTER> to end the command. Pick near P2 to continue, then press <ENTER>. This is what your command line should have looked like:

Command: _dimbaseline
Select base dimension:
Specify a second extension line origin or (Undo/<Select>): <pick P1>
Dimension text = 1.50
Specify a second extension line origin or (Undo/<Select>): <pick P2>
<Dimension text = 2.00
Specify a second extension line origin or (Undo/<Select>): <ENTER>

Your drawing should now look similar to the sample drawing. Check to see if you missed any dimensions.

Now you have dimensioned the drawing, save it and print it.

Next you want to copy everything over 12" to the right. Start the COPY command, and when asked to select objects, type ALL <ENTER>. Then copy it all 12" to the right.

What you want to do next is scale the copy of everything to double its existing size. Start the SCALE command. When asked to select objects, draw a window around the new set of objects and press <ENTER>. When asked for a base point, pick the bottom left corner of the border. Enter 2 for the scale factor. Your command line should look like this:

Command: SC <ENTER>
SCALE
Select objects: Other corner: 38 found
Select objects:<ENTER>
Base point:<Pick the Bottom Left Corner>
<Scale factor>/Reference: 2 <ENTER>

Perform a Zoom Extents (type Z <ENTER> E <ENTER>) at the command line. Now that everything is twice as large, Zoom in on your dimensions and you'll see that they have automatically adjusted to the new sizes! This is called associative dimensioning.

There are many different parameters you can change to get just the right look for your dimensions and text (use the DDIM command). This is will not be covered in this course.

For practice, you can try dimensioning some of your other assignments.

Even if your drawing is 100% accurate, it is still only as good as the dimensions. Some common mistakes when dimensioning are:

• Not using your Osnaps. If you don't get the exact endpoint of a line, then your dimension is wrong.
• Snapping to the wrong point. In detailed drawings, this can be easy to do if you aren't paying attention.
• Incomplete dimensions. If you miss one or two dimensions, you can delay the project while these numbers are located, new drawings made, delivered, etc..
• Confusing dimensions. Make sure that your dimensions don't overlap, or aren't too close, or otherwise unclear.

 View the video for Assignment 6 

(THE ABOVE FLASH IS WORK JUST YOU INSTALL FLASH PLAYER)

http://get.adobe.com/flashplayer/.

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