Why Every Feature Should Have a Tolerance

Today’s Question Line video covers a broad question we hear often at GD&T Basics:

Why should every feature on a drawing have a tolerance?

We often get pushback when people hear us say that every feature should have a tolerance. Designers worry about overcomplicating drawings, manufacturing worries about meeting tighter requirements, and inspectors imagine endless measurements and reports. 

But does assigning a tolerance to every feature really mean every dimension must be tightly controlled or inspected? 

In this video, Jason tackles a common misconception about tolerancing and explains why fully defining a drawing doesn’t have to mean overengineering it. Using a real-world part example, he explores the role tolerances play in communicating design intent, establishing clear acceptance criteria, and eliminating ambiguity between engineering, manufacturing, and quality teams. 

 

 

One of the key themes throughout the discussion is that tolerances should be driven by function. Engineers must understand how a part is used, what it mates with, and what requirements are truly critical before they can effectively define a drawing. This functional approach to tolerancing is a major focus of our GD&T Design course, where students learn a structured process for creating fully defined drawings, including how to select appropriate datums, and apply dimensions and tolerances based on a part’s functional requirements. 

Also in this video, Jason discusses what drawings don’t define, including which manufacturing processes or machines should be used to produce a part, what inspection equipment should be used, or how many parts should be inspected. Those decisions are typically left to the manufacturing and quality teams—but good engineers keep all of those downstream considerations in mind when creating a drawing. 

 

 

Whether you’re creating drawings, building parts, or inspecting them, this video offers a practical look at what it means to fully define a part without adding unnecessary complexity. And if you’d like to take a deeper dive into those topics, check out our GD&T Design course, where we teach a practical, step-by-step approach to creating functional, manufacturable drawings. 

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