True Position Calculator

The True Position Calculator determines the exact deviation of a hole or feature from its intended position based on geometric tolerances, ensuring precise alignment in manufacturing and engineering.

True Position Calculator for Holes

Maximum Material Condition Adjustment.
Example: If low limit is .250 dia. and hole is .255, then enter .005.

Results:

Radial True Position = 0.0071
Diameter True Position = 0.0142
With MMC = 0.0122

Demo Details: This is a sample calculation based on X = 0.005, Y = 0.003, and Diameter Adjustment = 0.002.


How the True Position Calculator Works

The True Position Calculator is a tool designed to calculate the positional accuracy of features, such as holes or pins, in manufacturing and engineering applications. It uses the concept of Geometric Dimensioning and Tolerancing (GD&T) to determine how far a feature deviates from its intended location.

Key Concepts

  1. Position Deviation (X, Y):
    • The user inputs the deviations (X and Y) of the actual position of the feature from its theoretical “basic” position. These deviations are measured in inches or millimeters.
  2. Radial True Position:
    • The radial true position is calculated using the Pythagorean theorem:Radial TP=X2+Y2​
    • This represents the straight-line distance between the actual position and the basic position.
  3. Diameter True Position:
    • The diameter true position is simply twice the radial true position:Diameter TP=2×Radial TP
    • This value is often used in GD&T to define a tolerance zone around the basic position.
  4. Maximum Material Condition (MMC) Adjustment:
    • If the feature has a size tolerance (e.g., a hole’s diameter), the user can input the additional size over the minimum limit. This adjustment accounts for bonus tolerances under MMC.
    • The final true position with MMC is calculated as:With MMC=max(0,Diameter TP−Diameter Adjustment)
    • If the adjustment exceeds the deviation, the result is zero, indicating the feature is within tolerance.

Why Use This Calculator?

  • Precision: Ensures accurate measurement of positional tolerances in manufacturing.
  • Efficiency: Simplifies complex calculations into a single, easy-to-use interface.
  • Compliance: Helps engineers and machinists adhere to GD&T standards, ensuring parts meet design specifications.

Example Use Case

A machinist measures a hole that is slightly off-center. They input the X and Y deviations (e.g., 0.005 and 0.003) and the additional diameter size over the minimum (e.g., 0.002). The calculator determines:

  • Radial True Position: 0.0071
  • Diameter True Position: 0.0142
  • With MMC: 0.0122

This information helps verify whether the part meets the required tolerances.