True Position

Definition

True position is a geometric dimensioning and tolerancing (GD&T) term that defines the exact location where a feature should be located in relation to its reference features. It specifies the allowable deviation from this exact location, ensuring that parts fit together correctly during assembly. True position is vital for ensuring manufacturing accuracy and functionality, particularly in complex assemblies where precise alignment of components is essential.

5 Must Know Facts For Your Next Test

1. True position is often represented by a circular tolerance zone on engineering drawings, indicating where the center of the feature must fall.
2. The size of the tolerance zone depends on the size of the feature being measured; larger features typically have larger tolerance zones.
3. True position applies not only to holes but also to any feature, such as slots or tabs, requiring accurate location for assembly.
4. Using true position helps reduce manufacturing costs by allowing for greater flexibility in part fabrication while still maintaining assembly requirements.
5. True position is a critical concept in industries such as aerospace and automotive, where precise part alignment can affect overall system performance and safety.

Review Questions

• How does true position contribute to the accuracy of mechanical assemblies?
  • True position ensures that each feature of a part is located precisely in relation to its reference features, allowing components to fit together accurately during assembly. By defining a specific location for features with an allowable deviation, true position promotes consistency in manufacturing. This accuracy is crucial for mechanical assemblies where misalignment can lead to functional issues, increased wear, or failure of the assembled system.
• Discuss the role of datums in establishing true position on engineering drawings.
  • Datums serve as reference points or surfaces that establish a framework for measuring the location of features on a part. When true position is specified, it relies on these datums to define the exact intended location of features. The accuracy of true position directly correlates with how well the datums are defined and used in the manufacturing process. A poorly chosen datum can lead to inaccuracies in feature placement, negatively impacting assembly and functionality.
• Evaluate how tolerances associated with true position can impact manufacturing processes and product quality.
  • Tolerances related to true position significantly influence manufacturing processes by determining how much variation is acceptable during production. Tight tolerances may require more precise machining techniques and quality control measures, potentially increasing production costs. Conversely, wider tolerances can allow for more flexible manufacturing methods but may risk compromising product quality if not carefully managed. Balancing these tolerances is essential for optimizing both cost efficiency and the integrity of final products.

Related terms

Geometric Dimensioning and Tolerancing (GD&T):

A system that uses symbols and annotations on engineering drawings to communicate the size, shape, form, and allowable variations of features.

Datum: A reference point, line, or surface from which measurements are made to establish the location of features on a part.

Tolerance Zone: The three-dimensional space within which a feature is allowed to deviate from its true position, defined by the dimensions specified in the drawing.