> ## Documentation Index
> Fetch the complete documentation index at: https://support.lumafield.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Cylindricity

> GD&T cylindricity of a cylinder feature, with no datum

Cylindricity constrains the form of a cylinder. In ASME Y14.5 the tolerance zone is the space between two coaxial cylinders, and the surface must lie between them. Cylindricity covers roundness, straightness, and taper together. It has no datum. A hole can be a true cylinder and still be in the wrong place; that place is [Position](/voyager/voyager-position). It can be a true cylinder and still lean; that lean is [Perpendicularity](/voyager/voyager-perpendicularity) or [Parallelism](/voyager/voyager-parallelism).

The Cylindricity Tool in [3D Auto-Dimensioning](/voyager/voyager-auto-dimensioning) evaluates one **cylinder** from the [feature set](/voyager/voyager-feature-extraction) — a hole or a pin — whether it was extracted or [authored](/voyager/voyager-manual-feature-authoring). A fillet is its own feature, not a cylinder.

<h2 id="what-the-number-means">
  What the number means
</h2>

The reported cylindricity is the radial width of the zone that contains the surface: the difference in radius between the outer and inner cylinders of the zone. The Viewport draws the deviation as a heatmap on the cylinder. The callout carries the value and a pass or fail state against the tolerance.

Cylindricity does not use the erosion control that [Flatness](/voyager/voyager-flatness) uses.

<h2 id="workflow">
  Workflow
</h2>

<Steps>
  <Step title="Select Cylindricity">
    Choose **Cylindricity** from the Toolbar in [Dimensioning Mode](/voyager/voyager-modes#dimensioning-mode), or right-click a cylinder and choose **Add cylindricity control…**.
  </Step>

  <Step title="Choose a cylinder">
    Click the cylinder. Eligible cylinders highlight on hover.
  </Step>

  <Step title="Set the tolerance">
    Enter the tolerance in millimeters.
  </Step>

  <Step title="Submit">
    Submit to add the control to the feature set. The heatmap and the callout appear on the cylinder.
  </Step>
</Steps>

<Tip>
  The tolerance can be edited after the control exists. The heatmap and the pass or fail state update without a new extraction.
</Tip>

<h2 id="interpreting-results">
  Reading the result
</h2>

The heatmap shows where the surface leaves a perfect cylinder. A band at one end is taper. A stripe along the length is a flat or a lobe. Use the callout controls to move the leader. The cylindricity value does not change.

<h2 id="related-pages">
  Related pages
</h2>

* [3D Auto-Dimensioning](/voyager/voyager-auto-dimensioning)
* [Feature Extraction](/voyager/voyager-feature-extraction)
* [Manual Feature Authoring](/voyager/voyager-manual-feature-authoring)
* [Flatness](/voyager/voyager-flatness)
* [Position](/voyager/voyager-position)
* [Perpendicularity](/voyager/voyager-perpendicularity)
* [Parallelism](/voyager/voyager-parallelism)
* [Direct Dimensions](/voyager/voyager-direct-dimensions)
* [Datum Definition](/voyager/voyager-datums)
* [Profile](/voyager/voyager-profile)
* [Voyager Modes](/voyager/voyager-modes)
* [Voyager Release Notes](/platform/voyager-release-notes)


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