# JSS3 BASIC TECHNOLOGY SCHEME OF WORK FOR FIRST TERM 2014/15 WEEK TOPIC

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JSS3 BASIC TECHNOLOGY SCHEME OF WORK FOR FIRST TERM 2014/15 WEEK TOPIC
CONTENT 1 ISOMETRIC DRAWING Definition and axes, isometric drawing of simple shaped blocks without curves 2 Isometric drawing Board practice 3 Oblique drawing Definition ,oblique drawing 4 Orthographic projection Principal planes (vertical and horizontal), angles of projection(1stand 3rd ), principal views (front, side and plan). 5 Placing principal views in quadrants, dimensioning techniques 6 One point perspective drawing Definition, principles, practise 7 Motions in engineering (linear) Definition, linear motion, lever arrangement to produce linear motion, use of slots and slides in mechanical systems. 8 Motions in engineering (rotary) Types9one way and reversible), principles of application, conversion of rotary motion to linear motion 9 Revision 10 Examination

CONTENT: TOPIC: ISOMETRIC DRAWING DEFINITION ISOMETRIC AXES
DIMENSIONING DRAWING OF A SIMPLE SHAPED BLOCK ISOMETRICALLY.

DEFINITION An isometric drawing can be defined as a form of pictorial drawing which is inclined at 30 degrees to the horizontal plane

The following Instruments are used in isometric drawing for speed and accuracy
Tee square Set square Rules French curves Etc

What is a simple solid? 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: Triangles, quadrilaterals, polygons, prisms, pyramids, cones, spheres and other solids such as tetrahedron, hexahedron, octahedron etc NOTE: CHECK Pg.23 EVANS BASIC TECH FORJSS BK.3

ISOMETRIC AXES An axis is the imaginary line that joins the centre of the ends of regular solid Right receding axis Left receding axis Vertical axis Isometric drawing is built around the isometric axes as shown below

ISOMETRIC VIEW

DIMENSIONING 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

Essential points to note when 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 their radius, R=50

Essential points contd.
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.

THE simple shaped block IS AN isometric DRAWING
50 20 35 20 80 ALL DIMENSIONS ARE IN MM

Evaluation 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 your note.

Assignment Reproduce and dimension this isometric block.
50 20 35 20 50 ALL DIMENSIONS ARE IN MM

SUBMMIT HARD COPY UPON RESUMPTION
THANK YOU

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