Learning Targets
- Distinguish nominal size from an acceptable size range.
- Calculate upper and lower limits from a stated tolerance.
- Classify measured samples and explain a possible functional consequence.
IED Unit 1 • Lesson 1.14
Tolerances
Focus question: Why do engineers allow some variation in measurements, but not too much?
Mission Briefing
Today’s Plan
Use this page with the lesson presentation and your engineering notebook.
Success Looks Like
The inspection decision follows calculated limits rather than visual judgment.
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Opening Prompt
Why can two parts have slightly different measurements and still both be acceptable?
Think first, then be ready to share a short response that connects the question to engineering communication.
Reveal: why this matters
Manufacturing cannot produce every feature at one exact value. A tolerance defines the range that still allows the part to perform its intended function.
Core Skill
What We Are Practicing
Nominal size is the target value for a feature.
Tolerance defines the allowed variation around the target.
A measurement is acceptable only when it falls within the calculated limits.
Lesson Interactive
Tolerance Decision Calculator
Enter a nominal size, bilateral tolerance, and measured value. The tool calculates the acceptable limits; you decide whether the sample passes.
Calculated Limits
Lower Limit19.850mm
Upper Limit20.150mm
Calculated StatusOversized
A part passes only when the measurement is within both limits, including the endpoints.
Your Task
Determine Whether Parts Meet Tolerance
Use stated nominal sizes and tolerances to evaluate sample measurements.
- Calculate the upper and lower acceptable limits for each assigned feature.
- Compare each sample with the limits and classify it as acceptable, undersized, or oversized.
- Explain one possible assembly consequence of an out-of-range sample.
- Recommend a reasonable tolerance for one additional feature and justify the choice.
Quality check: Every classification must be supported by shown calculations and units.
What You Will Submit
Tolerance and Inspection Analysis
Submit one completed analysis and one short engineering recommendation.
Submission standard: Include units and plus/minus notation; a nominal value alone is not an inspection limit.
Resources
Lesson Resources
Lesson 1.14 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.