---
title: "Why Do Engineering Drawings Use Tolerances Instead of Exact Dimensions?"  
description: "Why Do Engineering Drawings Use Tolerances Instead of Exact Dimensions?"  
author: "Laura Bennett"  
published: 2026-10-16  
canonical: https://answers.mindstick.com/qa/117722/why-do-engineering-drawings-use-tolerances-instead-of-exact-dimensions  
category: "Mix Category"  
tags: ["manufacturing", "mechanical engineering", "quality control"]  
reading_time: 1 minute  

---

# Why Do Engineering Drawings Use Tolerances Instead of Exact Dimensions?

On a manufacturing drawing, a dimension often comes with a permitted range rather than one exact number. I understand that real parts cannot be made with perfect precision, but how are those limits chosen in the first place?

For example, what determines whether a hole needs a very tight tolerance or can be allowed to vary more? I’m trying to understand how designers balance how the part functions against inspection time, machining difficulty, and cost.


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Original Source: https://answers.mindstick.com/qa/117722/why-do-engineering-drawings-use-tolerances-instead-of-exact-dimensions

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