Learning Targets
- Identify the dimensions needed to define overall size and feature location.
- Use dimension lines, extension lines, arrowheads, and symbols correctly.
- Audit a drawing for missing, duplicated, or ambiguous dimensions.
IED Unit 1 • Lesson 1.9
Dimensioning Basics
Focus question: How do engineers show the size of an object clearly in a drawing?
Mission Briefing
Today’s Plan
Use this page with the lesson presentation and your engineering notebook.
Success Looks Like
Another person can determine the required sizes without measuring the drawing itself.
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Opening Prompt
Why is a perfectly drawn shape still incomplete without dimensions?
Think first, then be ready to share a short response that connects the question to engineering communication.
Reveal: why this matters
The views communicate shape, but dimensions communicate the required size and feature locations. Without them, a fabricator would have to guess or scale the picture.
Core Skill
What We Are Practicing
Views communicate shape; dimensions communicate size and location.
Dimension lines, extension lines, arrows, symbols, and values work together.
Good dimensioning is complete without repeating the same information.
Lesson Interactive
Audit a Dimensioned Drawing
Inspect the sample drawing and identify all three problems that would make manufacturing or inspection less reliable.
A complete drawing states every required size and location once, without relying on scale.
Your Task
Dimension a Part for Manufacturing
Add a complete but nonredundant set of dimensions to a provided technical drawing.
- Identify the overall sizes and the information needed to locate each feature.
- Place extension and dimension lines outside the object whenever possible.
- Use diameter and radius symbols correctly for circular and curved features.
- Audit the drawing for missing, duplicated, crossed, or ambiguous dimensions.
Quality check: Every required size and location must be stated once, and no information should depend on scaling the drawing.
What You Will Submit
Fully Dimensioned Technical Drawing
Submit one completed drawing and one audit note.
Submission standard: Use one unit system consistently and do not place a dimension value on an object line.
Resources
Lesson Resources
Lesson 1.9 PowerPoint
Use the lesson slides for guided practice, interactive checks, and the exit ticket.
Introduction to Engineering Design
Return to the IED course hub for units, resources, certifications, and current course information.