Concentricity : GD&T Basics

Concentricity tolerance controls the central axis of a cylinder or sphere with respect to datum plane/axis. In another words, it controls median points on high precision cylindrical parts such as transmission gears.

LMC and MMC modifiers are not applicable with concentric tolerance.

Representation of Concentric Tolerance

Concentric Tolerance Zone

It makes a 3-dimensional cylindrical tolerance zone around datum axis. All the measured central points of circular feature must lie in this tolerance zone.

How To Measure Concentric Tolerance?

Concentric tolerance is very difficult to measure. That’s why, runout and position tolerance are more preferred.  

Step-1 : Identify part datum axis

Step-2 : As shown, fix the part on datum axis.

Step-3 : Plot the controlled surface outer profile using CMM.

Step-4: Determine the central points of plotted profile at various cross sections.

Step-5: Verify position of central points. All points should lie within given cylindrical tolerance zone.

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