Unit 2.Drawing applied to technology

What are we going to see in this unit? 2.1 Drawing tools and how to use them 2.2 Drafts and sketches 2.3 Drafting scale 2.4 Diedric system 2.5 Marking and standardizing

Unit 2.Drawing applied to technology

2.1 Drawing materials and instruments

Paper Paper is made of cellulose that is obtained from

trees The paper size that we use is A4 . It is the result

of dividing 1 m2 (A0) four times by half the longest side.

2.1 Drawing materials and instruments

Pencil A pencil is lead in a wooden casing. The

lead is made with graphite and clay

clay

Graphite

Lead

Wooden casing

2.1 Drawing materials and instruments

Pencil hardnessThe more clay it contains the harder the lead

will be. We use letter H for hard pencils and letter B for soft ones.

Hard: H Soft: B

Very hard Hard Medium Soft Very soft

6H 5H 4H 3H 2H H HB B 2B 3B 4B 5B 6B

less clayMore clay

Technical drawing

Artistic drawing

2.1 Drawing materials and instruments

Mechanical pencilsThey hold graphite lead. They can be used for

technical drawing if used with a soft lead.

ERASERSErasers are made of rubber; they absorb graphite and erase it.

2.2 DRAFT AND SKETCH

DRAFT: It is a free hand drawing (with just a pencil). We show an idea or object without totally defining it.

2.2 DRAFT AND SKETCH

ATTENTION! A DRAFT IS NOT A BAD

DRAWING AND A SKETCH IS NOT A GOOD DRAWING !!!!!!

2.2 DRAFT AND SKETCH

The sketch: It is a free hand drawing too, but it includes the measurements, therefore it shows the precise size and a shape similar to the final drawing.

measure

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2.2 DRAFT AND SKETCH

Activity: draw a sketch of your home cupboard.

2.2 DRAFT AND SKETCH

the Sketch

2.3 Drafting scale We define scale as the relationship

between the size of the drawing and the real object.

A model uses a reduction scale

2.4 Diedric system

2.4 Diedric systemThe diedric system represents the objects

using a perpendicular projection on a plane

2.4 Diedric systemThe projection or VIEW consists of drawing just

what we see when we are perpendicular to the object and to the plane

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2.4 Diedric systemTo define an object we only need 3 views, top, front and

profile: Top view: from the top of the object Front view: facing the object Profile view: from the side

Profile view

Top view

Front view

Front view

Top view

Profile view

2.4 Diedric systemDiedric RulesThe front is usually indicated with an arrowThe views distribution

The front is always on top of the top view The profile is situated the other way round,

that is, the left profile is situated on the right

front

top

Left profile Right profile

top

front

2.4 Diedric systemRemember: The same height: the object has the same height on the

floor and on the profile views The same width: on the front and on the top views The same depth: on the floor and on the profile views

2.4 Diedric systemExercise: Draw the front, left profile

and floor views of the class chair

2.4 Diedric system Exercise: Draw the front, profile and floor

views of the class chair

2.4 Diedric systemWhere do we have to be situated to see these objects like circles?

2.4 Diedric systemExercise 11: Complete the views of the following objects

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2.4 Diedric systemExercise 11: Complete the views of the following objects

2.4 Diedric systemExercise 11: Complete the views of the following objects

2.4 Diedric systemExercise 11: Complete the views of the following objects

2.4 Diedric system Non visible lines: when we know there is a hidden

line we have to draw it using a discontinuous line

hidden line

2.5 Marking and standardizingStandardizing is the group of rules

that defines technical drawing. For example:

For paper size we use the DIN rule: A0,A1,A2… The lines are:

Thick continuous lines: are used to outline objects Thick discontinuous lines: indicate hidden lines Thin continuous lines: are used for auxiliary measures

and reference lines

2.5 Marking and standardizing

Dimension line

Extension Line

Measure

Reference line

2.5 Marking and standardizingOutside thick

continuous line

a discontinuous line of medium thickness for a hidden edge

2.5 Marking and standardizing

Marking : indicating the real dimensions of the object

Vocabulary

Paper size Cellulose Clay, graphite, lead Hard and soft pencils Erasers, technical pencil Sixty and forty-five degree rules Sketch, draft, free hand drawing, measures Scale, real and drawn size, reduction, enlargement

scales To be reduced 100 times… Length, height, width Long, high, wide.