### Basic Tech lesson note

```JSS3 BASIC TECHNOLOGY
SCHEME OF WORK FOR FIRST TERM 2014/15
WEEK
1
TOPIC
ISOMETRIC DRAWING
2
3
4
Isometric drawing
Oblique drawing
Orthographic projection
5
Orthographic projection
6
7
One point perspective drawing
Motions in engineering (linear)
8
Motions in engineering (rotary)
9
10
Revision
Examination
CONTENT
Definition and axes, isometric drawing of simple
shaped blocks without curves
Board practice
Definition ,oblique drawing
Principal planes (vertical and horizontal), angles of
projection(1stand 3rd ), principal views (front, side
and plan).
Placing principal views in quadrants, dimensioning
techniques
Definition, principles, practise
Definition, linear motion, lever arrangement to
produce linear motion, use of slots and slides in
mechanical
systems.
Types9one way and reversible), principles of
application, conversion of rotary motion to linear
motion
TOPIC: ISOMETRIC DRAWING
 DEFINITION
 ISOMETRIC
AXES
 DIMENSIONING
 DRAWING OF A SIMPLE SHAPED BLOCK
ISOMETRICALLY.
An isometric drawing can be defined as a form of pictorial
drawing which is inclined at 30 degrees to the horizontal
plane
 Tee
square
 Set square
 Rules
 French curves
 Etc
A
simple solid is a firm object having length,
width and height.
 It has three principal dimensions enclosed by
surfaces.
 Examples of simple geometrical solids are:
pyramids, cones, spheres and other solids
such as tetrahedron, hexahedron,
octahedron etc
 NOTE: CHECK Pg.23 EVANS BASIC TECH
FORJSS BK.3
 An
axis is the imaginary line that joins the
centre of the ends of regular solid
Left
recedin
g axis
Right
receding
axis
Vertical axis
Isometric drawing is built around the isometric axes as shown
below
 This
is the selection of correct measurment,
the lettering and the positioning of the
dimensions on a drawing.
 Types of dimensioning:
 Chain dimensioning
 Datum dimensioning
 Dimensioning
are placed outside the outline
of the views
 Extension or projection lines are used to
indicate the length to be dimensioned.
 They are written above a horizontal lines and
on the left of vertical lines.
 It should be spaced on the drawing.
 Semi circles and arcs are dimensions using
 Do
not use centre lines and outlines as
dimension lines.
 Circles are dimensioned by their diameters
with symbol Ø.
 Never repeat dimensions on other views.
20
35
20
80
ALL DIMENSIONS ARE IN MM
 What
is isometric drawing?
 How many axes are found on isometric
drawing? Mention them.
 List any three essential points to note when
dimensioning.
 Reproduce and dimension the simple block in
 Reproduce
and dimension this isometric block.
50
20
35
20
50
ALL DIMENSIONS ARE IN MM
SUBMMIT HARD COPY UPON
RESUMPTION
THANK YOU
```