### Lesson Plan: Dimensioning in Technical Drawing
**Subject:** Technical Drawing
**Grade Level:** Senior Secondary 1
**Topic:** Dimensioning
**Duration:** 90 minutes
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#### Objectives:
1. Students will understand the purpose and importance of dimensioning in technical drawings.
2. Students will learn the different types of dimensioning (linear, angular, radial, aligned, and ordinate).
3. Students will practice basic dimensioning techniques through practical exercises.
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#### Materials Needed:
- Technical drawing textbooks
- Drawing boards
- T-squares, set squares, protractors, and compasses
- Pencils, erasers, and rulers
- Examples of dimensioned technical drawings
- Handouts with dimensioning guidelines
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#### Lesson Structure:
**Introduction (10 minutes):**
1. **Greeting and Attendance (2 minutes)**
- Welcome students to the class and take attendance.
2. **Engage:**
- Present an example of a technical drawing without dimensions and ask students what might be missing.
- Discuss briefly why accurate dimensioning is essential in technical drawings, emphasizing its role in conveying precise measurements.
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**Instruction (30 minutes):**
1. **Explain:**
- Define dimensioning and its purpose in technical drawing.
- Discuss basic rules and principles of good dimensioning, such as clarity, readability, and placement of dimension lines and numbers.
2. **Types of Dimensioning:**
- **Linear Dimensioning:** Lengths, widths, heights, and depths.
- **Angular Dimensioning:** Angles between intersecting lines.
- **Radial Dimensioning:** Radii of circles and arcs.
- **Aligned Dimensioning:** Dimensions placed parallel to the feature being measured.
- **Ordinate Dimensioning:** Series of dimensions from a common reference point.
- Illustrate each type with clear examples on the board or a projector.
3. **Dimensioning Guidelines:**
- Positioning of dimensions outside the drawing when possible.
- Avoiding redundant dimensions.
- Breaking dimension lines when they overlap.
- Using proper symbols and notations (e.g., diameter, radius, angle).
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**Activity (30 minutes):**
1. **Guided Practice:**
- Distribute handouts with several incomplete technical drawings.
- Guides students through the first example, demonstrating proper dimensioning techniques step-by-step.
2. **Independent Practice:**
- Assign students to complete the dimensioning on the remaining examples on their own.
- Monitor and assist students, providing feedback and correction as necessary.
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**Review and Assessment (10 minutes):**
1. **Collect Work:**
- Collect students’ drawings for assessment.
2. **Review Key Points:**
- Summarize the importance of proper dimensioning.
- Review the different types of dimensioning and their applications.
3. **Q&A Session:**
- Address any questions or uncertainties about the day's lesson.
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**Closure (10 minutes):**
1. **Homework Assignment:**
- Assign a set of additional drawings for students to practice dimensioning at home.
- Encourage students to follow the dimensioning guidelines and to bring their work to the next class for review.
2. **Preview Next Lesson:**
- Inform students that the next lesson will cover common errors in dimensioning and introduce more advanced techniques.
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#### Evaluation:
- Assess students’ understanding through their ability to correctly dimension technical drawings during the activity.
- Evaluate their homework for accuracy, neatness, and adherence to dimensioning guidelines.
- Provide individual feedback to help students improve.
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#### Additional Notes:
- Emphasize hands-on practice as a critical component of mastering dimensioning skills.
- Pair struggling students with more advanced peers for collaborative learning if necessary.
- Utilize multimedia resources (videos, interactive tools) where possible to enhance learning.
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This concludes the lesson plan for teaching dimensioning in technical drawing to Senior Secondary 1 students. The primary focus is on understanding the basics and developing practical skills through guided and independent practice.