Lesson Notes By Weeks and Term - Senior Secondary 3
Sectioning 1
Sectioning 1
TERM – 1ST TERM
WEEK SEVEN
Class: Senior Secondary School 3
Age: 17 years
Duration: 40 minutes of 5 periods each
Date:
Subject: Technical Drawing
Topic: SECTIONING 1
SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to
I.) Define sectioning
II.) Identify the uses of sectioning in Technical drawing
III.) Draw the various types of sections.
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 meaning and uses of sectioning. |
Students listens attentively to the teacher |
|
STEP 2 EXPLANATION |
Teacher identify and sketch the various types of sections. |
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 1
Sectional drawings are multi-view technical drawings that contain special views of a part or parts, which reveal interior features. Sectioning uses a technique that is based on passing an imaginary cutting plane through a part.
The process of sketching the internal configuration of an object by showing it cut apart is known as sectioning. Sectioning is used frequently on a wide variety of Industrial drawings.
The technique called section views is a very important aspect of design and documentation. It is used to
I.) Improve the visualization and clarity of new designs
II.) Clarify multiview drawings,
III.) Reveal interior features of parts, and
IV.) Facilitate the dimensioning of drawings.
Types of sections in Technical drawing
Cutting Plane
A surface cut by the saw in the drawing above is a cutting plane. Actually, it is an imaginary cutting plane taken through the object, since the object is imagined as being cut through at a desired location.
Cutting Plane Line
A cutting plane is represented on a drawing by a cutting plane line. This is a heavy long-short-short-long kind of line terminated with arrows. The arrows in show the direction of view.
Cutting plane placed in a drawing.
Section Lining
The lines in the figure above, which look like saw marks, are called section lining. They are found on most sectional views, and indicate the surface which has been exposed by the cutting plane. Notice that the square hole in the object has no section lining, since it was not changed by sectioning.
Different kinds of section lining is used to identify different materials. When an object is made of a combination of materials, a variety of section lining symbols makes materials identification easier. Here are a few examples:
Section lines are very light. When sketching an object or part that requires a sectional view, they are drawn by eye at an angle of approximately 45 degrees, and are spaced about 1/8” apart. Since they are used to set off a section, they must be drawn with care.
Full Sections
When a cutting plane line passes entirely through an object, the resulting section is called a full section Fig. 7 illustrates a full section.
It is possible to section an object whenever a closer look intentionally is desired. Here is an object sectioned from two different directions.
Half Sections
If the cutting plane is passed halfway through an object, and one-quarter of the object is removed, the resulting section is a half section. A half section has the advantage of showing both inside and outside configurations.
It is frequently used for symmetrical objects. Hidden lines are usually not shown on the un-sectioned half unless they are needed for clearness or for dimensioning purposes. As in all sectional drawings, the cutting plane take precedence over the center line.
Broken Out Sections
In many cases only a small part of a view needs to be sectioned in order to show some internal detail. In the figure below, the broken out section is removed by a freehand break line. A cutting plane line does not need to be shown, since the location of the cut is obvious.
Revolved Sections
A revolved section shows the shape of an object by rotating a section 90 degrees to face the viewer. The three revolved sections illustrated in the spear-like object of figure 12 show the changes that take place in its shape.
Offset Sections
An offset section is a means of including in a single section several features of an object that are not in a straight line. To do this, the cutting plane line is bent, or “OFFSET” to pass through the features of the part.
Removed Sections
A section removed from its normal projected position in the standard arrangement of views is called a “removed” section. Such sections are labeled SECTION A-A, SECTION B-B, etc., corresponding to the letter designation at the ends of the cutting plane line. Removed sections may be partial sections and are often drawn to a different scale.
EVALUATION: 1. Complete the section view.
CLASSWORK: As in evaluation
CONCLUSION: The teacher commends the students positively