AUTOCAD
FREQUENTLY ASKED QUESTIONS

 

 

NOTE: This is the FAQ related to ORTHOGRAPHIC DRAWINGS.  The FAQ for general AutoCAD questions is in the 2D drawings area.

 

 

Q-What is an orthographic drawing?

 

A-An orthographic drawing is a 3-view drawing of an object.  We often start with an object in isometric view and create an orthographic view of it.

 

Q-What are these three views?

 

A-The three views are TOP, FRONT and RIGHT SIDE. 

 

 

 

Q-How do we know what to put in each view?

 

We need to determine which view will be the front view, which will be the top view and which will be the right side view.

 

Below, the surfaces that are visible from the front are in white.  The surfaces that are visible from the top are in blue.  And the surfaces visible from the right are in red.

 

Notice how each view matches the surfaces of that view.

 

 

Q-How do we decide what the front view should be?

 

You can choose any side you want as the Front view but you should consider:

 

  • The object should be in a natural state (Example: We wouldn’t want to draw a car upsidown.)

 

  • The longer horizontal view is often best for the front view.

 

  • It is often best to choose a view that gives the most detail of the general shape of the object for the front view (Example: For a boat, the profile of the boat would be the best front view.)

 

 

Q-Can we place the views anywhere we want?

 

A-No.  The views need to be placed in a specific way.

 

The Top view appears directly above the Front view.

 

The Right side view appears directly to the right of the Front view.

 

 

Q-What should the gap between views be?

 

A-It doesn’t matter.  You decide what you think is best.  But make sure that the gap between the top and front view is the same as the gap between the from and right side view.

 

 

Q-When do I need hidden lines?

 

Hidden lines need to be used to show hidden surfaces that are parallel with the surfaces of your view.

 

Consider the image below. 

 

From the front, the viewer would actually be unable to see four missing parallel surfaces as seen below as well as the back.

We create hidden lines (shown in red) wherever those hidden surfaces do not lineup with other existing lines.  This would be the front view:

 

 

Q-Can you walk me through a drawing?

 

A-Here are the steps for the Control Bearing drawing:

 

STEP BY STEP

 

STEP 1 – DIMENSIONS

Start by figuring out the object’s length, height and depth.

 

 

STEP 2 – THE VIEWS

Decide which view is the front view.  For this drawing, the front is in lavender (below).


STEP 3 – BOUNDING RECTANGLES

Imagine bounding rectangles for each view (see below).

 

 

STEP 4 – RECTANGLES IN AUTOCAD

 

In AutoCad, draw each rectangle to represent your views.  In the example, notice that the front view is 128 by 41.5.  The top view is 128 by 50.  And the right side view is 50 by 41.5.  I decided to leave a gap of 15 between the rectangles. 

The Top View should appear above the Front View and the Right Side View should appear to the right of the Front View.

The example drawing should now look like this so far:

 

 

STEP 5 – THE DRAWING

Now, we can start the drawing.  I usually start with the easiest view and work my way to all three.  The order in which I choose to do this drawing may differ greatly from the order that another person would do the drawing.

 

In the example, I am starting with the top view.


Features on the top view line up with the front view.  So we can simply extend lines from the top view to the front view.  (We will delete these lines after.)

 

 

I then work on the front view. 

Notice the orange lines.  They represent a surface that is hidden from the viewer in that view.

 



I now erase the temporary lines between the views.

 



I can now do the Right Side View.  I can use measurements from the drawing or I can extend lines from the Front View.

I have decided to extend the line from the Front View that gives me the hidden line on the Right Side View.

 

 

We can actually also extend lines from the Top View to the Right Side View (and vice versa) by using a 45 degree diagonal line that starts at the top right of the Front View (like below).

 

 

And now I extend the lines that take a 90 degree turn when they hit the diagonal line.

 

With these temporary lines, I can now tell where the features on the Top View appear on the Right Side View.

 

I can now complete the Right Side View.

 

 

And now I remove the temporary lines.  I can also trim the parts of the initial rectangles that are no longer needed.

 

 

Done!