# Orthographic Drawing Lab

created by Lari Garrison

At the beginning of the school year our honors geometry class spends a few weeks learning some drawing techniques. We feel that being able to represent three-dimensional objects on two-dimensional paper is important not only for geometry class, but also for many careers which some of them may go into eventually. One technique we explore is orthographic drawing. It is used in industry a great deal, and usually done on computers. Our math classes do not have access to a computer lab with AutoCad, so I have created this lab to use next time we cover orthographic drawing. Students will produce a drawing on Sketch Pad following guidlines in a handout and submit it for evaluation (I will provide the stationary pad which they will use to get started). I also plan to follow up the lab with some questions about which they will think and write.

1. What characteristics of an object are better seen from an orthographic rather than an isometric view?

2. In isometric drawings of an object, two views, from opposite corners, are often shown. What is the purpose of showing these two views?

## Orthographic Drawing Lab Handout

Engineers often use technology to help them create more accurate orthographic drawings of items. Your mission today is to use Geometer's Sketch Pad to create a three-view orthographic drawing of the item shown. The "plate" is set up for you already. Once you open the template "orthographic" you need to follow the directions below:

1. From the FILE menu select SAVE AS. . .

2. Hit the delete button to erase the current name and type in the following (replacing the italicized part your name and initial, and the period you are in geometry) : BartS.per4.orthographic

3. Before hitting the save button make sure that you are saving into the correct folder. (Your teacher will explain).

Now that you have saved your plate you are ready to start work. The front view and top view have already been done for you, so all you have to do is draw the side view. Keep in mind that scale is important in this drawing. Someone somewhere is going to use your drawing to construct this piece, so your measurements must be accurate. Let one block edge = .5 inches on your sketch.

1. determine heights without measuring. The side view is the view in which an engineer communicates the depth and height of an object, and we will use the heights found in the front view and the depths found in the top view. To start the side view you should draw construction lines across the page from the front view over to the side view(this will give us the heights). To draw a line first you need to select two points using the shift key and the arrow tool and select line from the construct menu. Make sure that you have the line tool selected otherwise you will not be able to draw a line, but instead you will only be able to draw a segment or ray. Use the blue line as an example. You will want to draw lines across at all important heights.

2. determine depths without measuring. You will next need to draw construction lines from the top view to determine the depth of the object. This part will be a little more tricky than the first. You will want to start by changing the colors to pink under the display menu. There are a couple of lines drawn that you can use as examples (the pink ones). You will need to draw lines parallel to the pink line (in top view) at appropriate depths. To do this just pick two points that are at the same depth using the shift key and select line from the construct menu. When you have finished this task you need to mark the intersections of the new lines and the 45° line with points. To do this pick the point tool (under the arrow) from the left side of the screen and click on the intersections. Next you are going to construct a bunch of lines through the new points perpendicular to line RR'. To do this pick a point and line RR' (hold shift key down to select them both at the same time) and select perpendicular from the construct menu. Pretty easy, eh? Continue until you have perpendicular lines through all the points on the 45° line.

3. Here is where you have to use your big brain to finish the drawing. The construction lines have taken care of all the measurements for you. All you need to do is draw black segments and points over them to show what the actual side view looks like.

4. When you have finished, hide all your construction lines and points. DO NOT TRY TO DELETE THEM OR YOU WILL SCREW UP THE WHOLE DRAWING!! To hide something you select it and select HIDE from the display menu. You can hide more than one thing at a time by holding the shift key down while you select stuff.

Last thing. . .select the tool from the left side that looks like a pointing finger and point it at the text box at the top of the plate, click your mouse. Now type your name and period over the text that is there. When you have finished try a print preview (under the file menu) to see if everything fits on one page (if it doesn't click in the "scale to fit page" box). Now print a copy and hand it in. GOOD WORK!!

## Orthographic Drawing Lab Sketch

This is a gif copy of the SketchPad stationary pad which my students use to start their orthographic drawing.