Technical Drawing
Overview
Students will explore technical drawing basics, including reading and creating third-angle orthographic drawings, reading isometric drawings, the alphabet of lines, basic tools, and CADD basics.
A good introductory CADD program, offered by Autodesk is Tinkercad. Sixth, seventh, and eighth-grade students will use this program to develop a project to be printed on our 3D printer.
Third-Angle Projection
Example Tinkercad Drawing
Technical Drawing Basics
Technical drawing takes years to master. The information on this page will be useful for the basic technical drawing concepts that will be covered in class. To begin, technical drawing is a broad term that includes mechanical drawing, technical sketching, and CADD (computer-aided drafting and design). Mechanical drawing refers to precise accurate scale drawings made with the aid of drawing tools, such as a T-square, 30°- 60° triangle, 45°- 45° triangle, compass, protractor, scale, etc. A technical sketch is a fast drawing made without the use of tools, to show how something will look or function. Unlike regular sketching, technical sketching and drawings are not influenced in any way by opinion or emotion. CADD or computer-aided drafting and design involves the use of computer software to create technical drawings.
Technical drawing is known as the "language of industry" as it is an essential part of construction, electronics, and manufacturing. It is a "universal language." Since it is a graphic language (uses visual representations), it can be understood by anyone around the world. Even if you are not going into a technical field, drafting can be helpful. Drawing is often the best way to communicate an idea clearly and effectively. You have probably heard someone say, "let me just draw you a picture" because their idea was not being communicated clearly. A picture really is worth a thousand words!
Drafting is a graphic language. It has its own alphabet and grammar. With that being said, there are some basic types of lines and symbols you will see and use on drawings in class. The line types are known as the alphabet of lines. The lines below only represent a portion of the full alphabet of lines. Below that you will find a small selection of common symbols that will also be important to know.
Alphabet of Lines
Basic Lines
1. OBJECT LINES – Thick dark line use to show outline of object, visible edges and surfaces.
2. CONSTRUCTION LINE – Very light and thin line use to construct layout work.
3. DIMENSION LINE – Thin and dark lines use to show the size (span) of an object with a numeric value. Usually terminates with arrowheads or tick markings.
4. HIDDEN LINE – Short dash lines use to show non visible surfaces. Usually shows as medium thickness.
5. CENTER LINE – Long and short dash lines. Usually indicates center of holes, circles, and cylinders. Line is thin and dark.
6. EXTENSION LINE – Thin and dark line use to show the starting and ending of dimension.
Third Angle Projection - Drawing Layout
Orthographic projections are used by engineers to represent a three dimensional shape on paper. The object is drawn using multiple two dimensional views. Below, you will see the proper layout of views in a third angle orthographic projection. The views must be laid out in the correct order. The drawing below on the right shows the primary views (front, top, right-side) in the blue box. They are the most common views used in technical drawings. Also, in that drawing you can see how the dimensions carry from view to view (H= height, W= width, and D= depth).
When drawing orthographic projections, the front view is always drawn first. All other views are placed from that view.
Common Drafting Symbols
