Technical drawing (by: Sherief Elmetwali)

Tools of Technical Drawing

1

Definition of Technical Drawing

Technical drawing describes the process of producing a

pictorial representation of a designer or engineer's vision into

a physical form. Technical drawings serve as a guide or plan to

the construction of whatever is represented in the drawing.

Technical drawings use graphics to show details. In

other words, they convert ideas into physical form. Also

known as drafting, technical drawing is done using a

two-dimensional or three-dimensional depiction.

2

The Purpose for Technical Drawings

The purpose of a technical drawing is to clarify an

idea and to translate that idea into a common

graphical language.

Technical drawings fulfill the purpose of idea

translation through the application of a variety of

methods and visual conventions.

3

History

• Since the 18th century, specific disciplines of technical

drawing have developed, and during the 20th century,

these became aided by the use of computers.

Types• Technical drawing can be divided into four main

disciplines or types: construction, cutaway, exploded

view and patent

4

Tools Used for Technical Drawings1. Drafting Tables

2. Rulers and Squares

3. Curve Templates and Compasses

4. Lettering Guides

5. Drawing Pencils

6. Inking Pens

7. Drafting Machines

8. CAD: Computer Aided Design

5

Drafting Tables

Draftsmen create technical

drawings using a tilting table.

Parallel rulers on each side of

the drawing surface align the

drawing paper and provide

horizontal and vertical guides

for drawing.

6

Rulers and Squares

7

Using a T-square and clear plastic triangle, draftsmen create lines. Common triangles they use are an eight inch triangle with forty five and ninety degree sides and a ten inch triangle with 30- and 60-degree sides. Draftsmen measure dimensions with triangular shaped rulers that have different scales on each of three surfaces.

Curve Templates and Compasses

8

• Draftsmen create curves using

irregular curve templates made

of clear rigid plastic. They draw

circles and portions of circles

called arcs with an adjustable

compass and calculate angles

from 1 degree to 180 degrees

with clear plastic protractors

Lettering Guides

9

•Lettering templates guide the

draftsman in the execution of

uniform lettering throughout the

drawing. As a matter of common

practice most creators of technical

drawings hand letter in personally

developed styles that identify their

work as clearly as fingerprints.

Drawing Pencils

•Most draftsmen use sharp 2H and

4H pencils for drawing. Pencils may

be wooden or mechanical pencils

with replaceable leads. They utilize

erasing shields and soft gum or

nylon erasers to make corrections.

10

Inking Pens

11

Technical drawings created in

pencil are usually over-traced with

ink to render durable final

drawings. Early inking pens

consisted of a mechanical device

with an adjustable nib. Modern

disposable inking pens have built

in ink reservoirs and are available

in many point widths.

Drafting Machines

12

• Early drafting machines date back to Italy in 1913. Modern drafting machines combine horizontal and vertical rulers or scales and a protractor head that allows adjustment of the rulers to required angles for drawing. The device is permanently attached to the drawing board and uses a pair of connected arms to move freely around the drawing surface.

CAD: Computer Aided Design

13

• Drawings and designs using computer software drastically reduce hand and machine drafting, especially in the professional sectors. Lower drawing cost and greater degrees of accuracy dictate increasing use of CAD as a primary tool for creating technical drawings. Large computer screens for creating designs and plotters for printing large technical drawings are replacing traditional technical drawing tools. Colleges and trade schools offer CAD training to a growing number of specializing technicians who are replacing conventional draftsmen in the drafting room.

CAD Application

14

Uses of Technical Drawings• Construction drawings are made for defining engineering

items and are made with standardized conventions for layout and appearance reasons.

• Technical illustrations use illustrations to communicate visually technical information, for a nontechnical audience.

• Cutaway drawings are technical illustrations where surface items of three-dimensional model are removed selectively to make internal features

• An exploded view drawing shows how parts fit together in an assembly. Patent drawings are technical renderings of patent inventions, showing the nature of the invention. It shows all the invention's features .

15

Technical drawing methods

• a quickly executed freehand drawing that is not

intended as a finished work. In general, a sketch is a

quick way to record an idea for later use. Architect's

sketches primarily serve as a way to try out different

ideas and establish a composition before

undertaking a more finished work, especially when

the finished work is expensive and time consuming.

16

1- Sketching

Technical drawing methods

• The basic drafting procedure is to place a piece of

paper on a smooth surface with right-angle corners as

a drawing board. A sliding straightedge known as a T-

square is then placed on one of the sides, allowing it

to be slid across the side of the table, and over the

surface of the paper. the drafter uses several tools to

draw curves and circles.

17

2- Manual using instrument

Technical drawing methods

18

2- Manual using instrument

Technical drawing methods

• Today, the mechanics of the drafting task have largely been

automated and accelerated through the use of computer-

aided design systems (CAD).

• There are two types of computer-aided design systems used

for the production of technical drawings" two dimensions

("2D") and three dimensions ("3D").

• Both 2D and 3D CAD systems can be used to produce

technical drawings for any discipline.

19

3- Computer aided design

Applications for technical drawing

• The art and design that goes into making buildings is

known as architecture. To communicate all aspects of

the design, detailed drawings are used. In this field,

the term plan is often used when referring to the full

section view of these drawings. Architectural drawings

describe and document an architect's design.

20

Applications for technical drawing

• The art and design that goes into making buildings

is known as architecture. To communicate all

aspects of the design, detailed drawings are used.

In this field, Architectural drawings describe and

document an architect's design.

21

1- Architecture

Applications for technical drawing

22

2- Engineering

• Engineering drawings generally deal with mechanical

engineered items, such as manufactured parts and

equipment.

• The end goal of an engineering drawing is to convey

all the required information that will allow a

manufacturer to produce that component.

Summery

Importance of Technical Drawing• Technical drawing allows efficient communication

among engineers and can be kept as a record of the

planning process. Since a picture is worth a thousand

words, a technical drawing is a much more effective

tool for engineers than a written plan.

23