Engineering Drawing - Sketching

FIRST ANGLE & THIRD ANGLE PROJECTION

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FIRST ANGLE & THIRD ANGLE PROJECTION

Engineering Drawing
Introduction to Engineering Drawing

1.3 Line Type

TYPE CHARACTERISTIC LINE
Visible
are continuous lines, thick &
Hidden dark, used to depict edges
directly visible from a
Center particular angle.

are short-dashed lines,
thinner than visible, used to
represent edges that are
not directly visible
are alternately long- and
short-dashed lines used to
represent the axes of
circular features.

ENGINEERING
DRAWING
DFV10032

LEARNING OUTCOME

At the end of this lesson student should be
able to:
1. Define by own word the concept for the four
types of sketches.
2. Differentiate the concept for the four types of
sketches.
3. Create isometric sketches from selected object.
4. Create oblique sketches from selected object

i) Orthographic sketching
ii) Axonometric sketching
iii) Oblique sketching
iv) Perspective sketching

2.1.1 Orthographic Drawing

A system that allows you to make a two-
dimensional drawing of a three-dimensional
object

2.0 0

2.8 8 5 .13
1.25
1.6 3
Ø1.5 2 45 °

2.25 3.5 0
2.5 0
1.5 0

Viewing Objects

• A box is formed by six
mutually
perpendicular planes
of projection that are
located around the
object

Viewing Objects

• Lines are formed on the planes by projecting the
edges of the object onto the planes

– These images are called
“views”

– There are six views
formed by the planes of
a box

Viewing Objects

• Unfolding the box produces an
arrangement of the six views

TOP

BACK L.SIDE FRONT R.SIDE

BOTTOM

Viewing Objects

• Each view is placed in a
constant location relative to
the other views

• Each view must be placed in
its correct position

• Views and features must be
aligned

Choosing Views

• Most commonly used 2.00
views
TOP VIEW
– Front View 5.13
– Top View 2.88 1.25
– Right Side View 1.63

Ø1.52 45°

2.25 3.50
2.50
1.50

• Most descriptive view is FRONT VIEW RV. ISEIWDE
typically designated as
the Front View

2.1.2 AXONOMETRIC SKETCHING

Axonometric projection is a parallel
projection technique to create a pictorial
drawing of an object by rotating the object
on an axis relative to a projection plane

2.1.3 AXONOMETRIC SKETCHING cont’d

Type of axonometric drawing

1. Isometric a Axonometric axis
bc All angles are equal.

2. Dimetric a Axonometric axis
bc Two angles are equal.

3. Trimetric a Axonometric axis
bc None of angles are
equal.

2.2 ISOMETRIC SKETCHES

60o 60o

30o 30o
Isometric Axis

Isometric means equal measure
All planes are equally or proportionally tilted
All the major axes (X, Y, Z) are 120 degrees apart

15

2.2 ISOMETRIC SKETCHES cont’d

Main purpose of isometric view is to provide a pictorial view which
reveals as much detail as possible

Figure shows different isometric view of the same block

2.2 ISOMETRIC SKETCHES cont’d

STEPS IN MAKING ISOMETRIC SKETCH FROM
ACTUAL OBJECT

1. Place the object in the position which its shape
and features are clearly seen.

2. Define an isometric axis.
3. Sketching the enclosing box.
4. Estimate the size and relationship of each

details.
5. Darken all visible lines.

2.2 ISOMETRIC SKETCHES cont’d

STEPS IN MAKING ISOMETRIC SKETCH
FROM ACTUAL OBJECT

STEPS
1. Positioning object.
2. Select isometric axis.
3. Sketch enclosing box.
4. Add details.
5. Darken visible lines.

2.2 ISOMETRIC SKETCHES cont’d

STEPS IN MAKING AN ISOMETRIC SKETCH
FROM DRAWING

2.2 ISOMETRIC SKETCHES cont’d

STEPS IN MAKING AN ISOMETRIC SKETCH
FROM DRAWING



EXERCISE 1
Sketch an Isometric Drawing

SOLUTION

EXERCISE 2
Sketch an Isometric Drawing

SOLUTION

EXERCISE 3
Sketch an Isometric Drawing

SOLUTION

EXERCISE 4
Sketch an Isometric Drawing

SOLUTION

EXERCISE
Sketch an Isometric Drawing

SOLUTION

2.4 Sketch an Isometric View cont’d

EXERCISE!!!!!

Q1: From the drawing below, sketch the isometric view.



2.4 Sketch an Isometric View cont’d

EXERCISE!!!!!

Q2: From the drawing below, sketch the isometric view.



ORTHOGRAPHIC SKETCHING



Intersections & Tangencies

• Where a curved surface is tangent to a plane
surface, no line should be shown where they
join

NO LINE
NO
LINE

Intersections & Tangencies

• Where a plane surface intersects a curved
surface, an edge is formed

LINE
LINE

Intersections & Tangencies

• Where the plane surface is horizontal or
vertical, exceptions to these rules may occur

LINE

VERTICAL
SURFACE

EXERCISE 1
Sketch an orthographic drawing

ANSWER
Sketch an orthographic drawing

EXERCISE 2
Sketch an orthographic drawing

ANSWER
Sketch an orthographic drawing

EXERCISE 3
Sketch an orthographic drawing

ANSWER EXERCISE 3
Sketch an orthographic drawing

2.1.4 OBLIQUE SKETCHING

Oblique drawings provide a quick way to
sketch an object and represent the three
dimensions of height, width and depth.

Oblique drawings have only one receding
axis. This axis can be drawn at angle 30°,45°
or 60° (usually 45°).

45o 60o
30o

2.3 OBLIQUE SKETCHES

Object is not rotated
Object remains with a major face parallel to projection
plane
Axis of height and width remains at 90 ⁰.
Axis of depth can vary at selected angle 30 ⁰, 45⁰ and 60⁰
(usually 45⁰).

45 ⁰

2.3 OBLIQUE SKETCHES cont’d

STEPS IN MAKING OBLIQUE SKETCH FROM
ACTUAL OBJECT

D

45°

2.3 OBLIQUE SKETCHES cont’d

STEPS IN MAKING OBLIQUE SKETCH FROM
DRAWING