Lesson Notes By Weeks and Term - Senior Secondary 3

Sectioning 2

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TERM – 1ST TERM

WEEK EIGHT

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Technical Drawing

Topic: SECTIONING 2

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

I.) Describe the general principles of sectioning in Technical drawing

II.) Discuss sectioning lines and symbols.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

STEP 1

INTRODUCTION

The teacher explains the general principles of sectioning in Technical drawing.

Students listens attentively to the teacher                                                                         

STEP 2

EXPLANATION

Teacher identify the sectioning lines and symbols and discuss their characteristics.

Students exhibit attentiveness and active engagement

STEP 3

NOTE TAKING

The teacher writes a summarized

note on the board

The students

copy the note in

their books

 

NOTE

SECTIONING 2

General principles of sectioning

  1. A sectional view represents the part of an object remaining after a portion is assumed to have been cut and removed.
  2. The exposed cut surface is then indicated by section lines.
  3. Hidden features behind the cutting plane are omitted, unless required for dimensioning or for definition of the part.

 

In the figure above, the lines of the edges between surfaces on the rear side of the part, shown as hidden lines on the non-cut multiview drawing, disappear from the section view.

Section lines and symbols

Section lines, or hatching, that represent the cut surface usually consist of thin parallel lines, as shown below, drawn at an angle of approximately 45° to the principal edges or axes of the part.

For most purposes, the general use symbol of cast iron is used. When it is desired to indicate differences in materials, for example on assembly drawings involving a variety of materials, other symbolic section lines may be used.

If the section lines appear to be parallel, or nearly so, to one of the sides or features of the part, you should choose other than 450 angle. Section lines should not run parallel or perpendicular to the visible outline.

The general purpose or cast iron section line is drawn at a 45⁰ angle and spaced 1/16" (1.5mm) to 1/8" (3mm) or more depending on the size of the drawing.

I.) In all sections of a single component, section lines should be similar in direction and spacing, but adjacent parts should be section-lined in different directions, angles, or spacing.

II.) Section lines should be thinner than visible lines.

III.) Do not run section lines beyond the visible outlines or stop them too short.

 

IV.) Thin elements should not be sectioned.

EVALUATION: 1. Discuss the principles of sectioning in Technical drawing.

  1. Describe the characteristics of section lines.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively