How To Read Tolerances

how to read tolerances

Knowing how to read tolerances can help you understand the intricacies of a part and the manufacturing methods it will require. Put simply, tolerance is a measurement (generally calculated in fractions of an inch) that specifies how much a given feature of a part may deviate from its specified measurement, and is the difference between the upper (maximum) and lower (minimum) limits. For example, if a part is specified as 3” with a tolerance of .2”, then completed parts measuring between 2.8” and 3.2” would be accepted. Completed parts that measure 2.79” and shorter, or 3.21” or larger, would not be acceptable.

On a part design, tolerances can be shown in several ways:

Why Are Tolerances Important?

Variations are inherent to all manufactured parts, but tolerances are used to control that variation, particularly in mating parts of an assembly. In addition to greater consistency, one of the benefits is that it permits interchangeable parts, allowing you to replace individual parts.

Tolerances also ensure the proper performance of your parts. If parts don’t meet tolerances, they can cause a number of issues in their end use applications. Because tolerances can vary depending on materials and manufacturing methods, it is important to work with an experienced manufacturer who understands the different plastics available for your part and the different tolerances those plastics can sustain.

Key Terms

In order to know how to read tolerances, you need to understand the terminology involved. Important terms include:

Tight Tolerances Are Our Specialty

At Reading Plastic, we’re experts at tight tolerances, providing high-quality precision parts to our clients for over three decades. We help you select the right plastic for your part and machine your parts to meet any requirements and deadlines. Call us today at 610-926-3245 or request a quote.

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