Molding Tolerances Chart | Decatur Mold
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Molding Tolerances Chart

Molding Tolerances Chart

To most people, plastic is simply plastic, the material that makes up shopping bags and household products. Those in the commercial and industrial manufacturing fields, however, know that the field of plastics is expansive and diverse.

There are thousands of different plastics, with more constantly being developed. When choosing the right type for your specific application, various considerations should be taken into account — different plastics are derived from different raw materials, synthesized with different methods, feature different physical properties, and are suitable for different uses.

Another variable to consider— one of the most important, in fact —  is the tolerances that can be held.


A tolerance is the measurement — usually calculated in fractions of an inch — specifying how much a given feature of a part may deviate from the specified measurement. For example, if an injection molded part is specified to be 1 in. long with a tolerance of 0.1 in., completed parts between 0.9 in. and 1.1 in. long would be acceptable; completed parts that are 0.89 in. or shorter or 1.11 in. or longer would not be acceptable.

Tolerances are set to ensure the proper performance of your part; parts out of tolerance can cause any number of issues in their end application. Tolerances can also vary depending on materials and processing methods.

Because of this, designing a part and selecting its material and production method can be a challenging process.

Balancing Tolerance and Cost

molding-tolerance-chartThe tighter the specified tolerances of a part, the more expensive that part will be to produce. Why? To put it simply, maintaining tighter tolerances requires more work.

Producing parts to tighter tolerances often requires specialized tools and equipment, which are more expensive to purchase and operate. Both tooling and completed parts must be subjected to more thorough and frequent quality assurance checks, which also add to costs.

Additionally, parts with tighter tolerances are rejected more often for being out of tolerance. This leads to more raw material requirements, higher scrap rates, and lower yields of completed parts, all of which add to production expenses.

Find the Right Tolerance

Finding the correct tolerances for your parts can be a challenge. Understanding the different plastics that are available for manufacturing your part — and, more importantly, the different tolerances that each of those plastics can maintain — will ensure a successful end product.

Decatur Mold has been an industryleading injection molder since 1966. Over our 50 years of experience, we have developed extensive knowledge of common molding plastics and the tolerances they maintain. We’ve collated this knowledge into a useful, easytoread guide, our Molding Tolerances Chart.

Download our Molding Tolerances Chart  and learn what tolerance is right for your project’s material , or click the button below for more information.