In this case, a tolerance to be maintained is described by two parallel planes or straight lines.
These are spaced at the specified distance and are parallel to the specified reference.
A measured value must lie within these planes or straight lines.
For cylindrical moldings, the tolerance zone is formed by a cylinder with the diameter of the specified tolerance value.
The axis of the cylinder needs to be parallel to the reference.
![Parallelism in Plastic Industry Parallelism in Injection Molding](https://www.plexpert.ca/wp-content/uploads/2021/12/Parallelism.png)
Quality assurance: The axis of the hole must be within a cylinder of 0.01mm.
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.