Technological Design - Technical Drawing

Objective

The objective of this unit is for the student to understand the purpose of technical drawing with product designs in engineering and architecture. The student will know how to measure, draw different views (orthographic, isometric, oblique, and perspective) of geometric objects with dimensions using drafting tools with standard technical drawing skills used among professionals. Students will use problem-solving skills to recreate a view of a geometric object into a different view.

Technical drawing is apart of the design stage. A product always begins at the design stage before it goes into production. All technical drawing has many standards so that one person's drawing of an object will be the same as another person's drawing of the same object.

Reference

Walker, J. R., Exploring Drafting. Tinley Park, Illinois: Goodheart-Willcox. 1996.

Measuring

The following drawing is one inch on a scale. As you can see, the inch is divided into 16ths, meaning there is 16 divisions. You can also problem solve that an inch can be divided into 8ths, 4ths, and halves.

 

Drafting Tools

This picture shows all the drafting tools needed to perform quality standard technical drawings.

 

T-Square is used for squaring the paper with the table, drawing horizontal lines, and placing angles along the top edge of the T-square for vertical, 30 deg., 45 deg., and 60 deg. lines.

The drawing board is the surface the paper needs to be squared upon.

The masking tape is used to tape all four corners of the paper to the table.

45 deg. triangle is used to create 45 deg. lines and vertical lines.

30 deg. - 60 deg. triangle is used to create 30 deg., 60 deg., and vertical lines.

The scale is used to measure lines precisely. It has different scales for different proportions. For a normal ruler, find the scale that indicates a "16" for represents 16 divisions of an inch.

Dividers are another way of measuring by placing the dividers along a scale to find a measurement and then placing the dividers on the paper.

The pencil is your drawing tool. Different shades of pencil lines represents different types of lines.

Protractor is used to find other angles which the triangles cannot.

The compass is used to create circles, arcs, and ellipses. To draw an arc, circle, and ellipses, the point of the compass should be placed at a circles center, the pencil edge should be placed at the end of the radius.

The French curves are used to draw complicated curves.

The eraser is used to erase all unnecessary lines like guide lines and mistakes.

The erasing guide helps the drafter erase only lines that need to be erased - not accidentally erasing others.

The pencil pointer is sand paper to keep the pencil edge sharp.

The dusting brush is used to keep the paper and table clean of eraser debris.

Notice the angles on each corner of the triangles.

Set Up

To begin drafting, the paper needs to be square with the table. Place the T-square tight against the side of the table. Place the bottom edge of the paper along the top edge of the T-square. Make sure the bottom edge is aligned with the top edge of the T-square. Tape the top two corners of the paper down with masking tape. Move the T-square away and tape the bottom two corners of the paper. The paper is now square with the table. All your vertical lines and horizontal lines will now be parallel with the paper's edges.

 

 

Lettering

Standard lettering for technical drawing is called Gothic lettering. All letters in a word are capitalized and squared. Below is an example of Gothic lettering.

Lines

Guide lines and construction lines are drawn very lightly. Construction lines are used to block in drawings, while guide lines are used for lettering. They may be erased, if necessary, after they have served their purpose.

Border lines are the heaviest line used in drafting. Just as the name suggests, border lines represent the border created for the drawing.

Object lines or visible lines are used to outline the visible edges of the object being drawn. They should be drawn so that the views stand out clearly on the drawing. All of the visible object lines on the drawing should be the same darkness. Object lines are dark lines but a bit lighter than border lines.

Dimension lines are usually capped at each end with arrowheads and is placed between two extension lines. The dimension line is a light line but a bit darker than construction lines.

Extension lines are the same darkness as dimension lines. It extends the dimension beyond the outline of the view so that the dimension can be read easily.

Hidden lines are used to show the hidden features of the object. It is drawn the same darkness as a object line and is composed of short lines approximately 1/8 in. long separated by spaces approximately 1/16 in.

Center lines are used to indicate the center of symmetrical objects. It is a dark line which is a bit lighter than a object line composed of alternate long (3/4 in.) and short (1/8 in.) dashes.

Cutting plane is line as a object line. It is used to indicate where the sectional view will be taken.

Section lines are used when drawing the inside features of an object. They indicate material cut by the cutting-plane line, and also indicate the general classification of the materials. The lines are dark but a bit lighter than object lines.

Borders & Name Block

Below is an example of how a the paper for a drawing should be bordered. Disregard the hole punches in the paper. The border lines are 1/2 in. from the edges of the paper. The name block is another 1/2 in. Remember that lettering is in Gothic style. Create guide lines for the lettering 1/8 in from the top and bottom of the name block. Place lettering in between the guide lines and then erase the guide lines.

Centering

The purpose of centering is for the entire drawing to be placed in the center of the borders and evenly spaced.

To begin, find the center of the borders by cris-crossing from one corner to the opposite corner. Where the lines cross is the center of the border.

For orthographic views, for the horizontal center, find the total horizontal for the object by adding the length and width of the object plus an amount for spacing between the front and side views. Take the answer and divide by 2. This is the amount to measure from the center point to the left and right along a horizontal construction line. For the vertical center, find the total vertical for the object by adding the height and width of the object plus the same amount for spacing between the front and top view. Take the answer and divide by 2. This is the amount to measure from the center point up and down along a vertical construction line. These points represent the outer edge of the drawing. Create a box with construction lines.

For isometric and oblique views, find the total width of the object and divide by 2. Draw a construction line 30 deg. from the center down and to the left that measurement. This represents the center of the front surface of the object.

For perspective views, find the total width of the object and divide by 2. Draw a construction line to the vanishing point from the center down and to the opposite of the vanishing point that measurement. This represents the center of the front surface of the object.

Orthographic

An orthographic view is a method of showing a three-dimensional object in two dimensions by displaying the front, top, and side view. Each view is evenly in line with each other. The front view is located on the bottom left. The top view is directly above the front view. The side view is directly to the right of the front view.

 

When given only two out of three views, the student will have to find the third view in an exercise. To find the top or side view, a 45 deg. construction line technique is used. The following is an orthographic drawing with the 45 deg. construction line included.  

 

Isometric

A three-dimensional pictorial drawing in which the horizontal axes form a 30 deg. angle with a true horizontal line.

 

 

Oblique

A pictorial drawing in which the front view of an object is shown as true size and shape. The top and side view is at 30 deg. angle.  

 

 

Perspective

A pictorial drawing in which lines moving "away" from the viewer converge.

 

 

 

Measuring

The following will assess the students understanding of measuring by filling in the measurements of the distance between the extension lines in the blank between the dimension lines.

 

 

Orthographic Packet

In the orthographic packet, the student is given 2 of 3 orthographic views and must find the third view by transferring construction lines to find the front view or transferring construction lines and using the 45 deg. construction line technique to find the top or side view.

 

Orthographic Drawing 1, Isometric Drawing 1, Oblique Drawing 1, & Perspective Drawing 1

 

Recreate both orthographic drawings as an orthographic, isometric, oblique, and perspective drawing.

 

 

 

Orthographic Drawing 2, Isometric Drawing 2, Oblique Drawing 2, & Perspective Drawing 2

 

Recreate both orthographic drawings as an orthographic, isometric, oblique, and perspective drawing.

 

Orthographic Drawing 3, Isometric Drawing 3, Oblique Drawing 3, & Perspective Drawing 3

Recreate the isometric drawing as an orthographic, isometric, oblique, & perspective drawing.