13.1 Circular and Total Runout

ASME GDTP Senior Level Exam

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1 Introduction & Exam Overview

1.1 Current Exam Facts 1.2 Senior Level vs Technologist and Y14.5 Revisions 1.3 How to Use This Guide and Study Strategy 1.4 The Y14.5-2018 Senior Exam and What Changed from 2009

2 Dimensioning and Symbology

2.1 Y14.5 Dimensioning Rules, Limits, and Fits 2.2 Basic Dimensions and Their Role 2.3 Feature Control Frame Structure and Reading 2.4 GD&T Symbols, Modifiers, and Communication 2.5 Screw Threads, Gears, and Splines 2.6 Angular Surfaces, Tapers, Radii, and Special Tolerance Cases

3 Datum Referencing I: Selection and Precedence

3.1 Functional Datum Feature Selection 3.2 Datum Precedence and Degrees of Freedom 3.3 Datum Targets 3.4 Datum Feature Simulators

4 Datum Referencing II: Modifiers and Shift

4.1 Multiple Datum Features and Datum Reference Frames 4.2 RMB, MMB, and LMB on Datum Features 4.3 Datum Shift Behavior 4.4 Planar vs Datum Feature of Size

5 Datum Referencing III: Setup and Calculations

5.1 Inclined and Translated Datum Features 5.2 Inspection Setup and Datum Establishment 5.3 Datum Calculation Walkthrough 5.4 Customized Datum Reference Frames and Rotational Constraint 5.5 Free State, Restrained Condition, and Nonrigid Parts

6 Form Controls

6.1 Flatness and Straightness 6.2 Circularity and Cylindricity 6.3 Rule #1, Form, and Size

7 Orientation Controls

7.1 Parallelism, Perpendicularity, and Angularity 7.2 Orientation Zones and Material Modifiers 7.3 Avoiding Unnecessary Orientation and Over-Control

8 Location I: Position and Boundaries

8.1 Position Tolerancing and True Position 8.2 Virtual and Resultant Condition 8.3 Bonus Tolerance at MMC and LMC

9 Location II: Application and Modifiers

9.1 Selecting MMC, LMC, and RFS by Function 9.2 Fixed and Floating Fastener Formulas 9.3 Projected Tolerance Zones 9.4 Coordinate Conversion and Appendix B Position Calculations

10 Location III: Patterns and Allocation

10.1 Composite Position Tolerancing 10.2 Patterns, Simultaneous Requirements, and Multiple Segments 10.3 Slots, Tabs, and Tolerance Allocation 10.4 Coaxial Feature Controls, Concentricity, and Symmetry

11 Profile I: Fundamentals and Strategy

11.1 Profile of Line and Surface 11.2 Defining the True Profile 11.3 Datum-Referenced Profile Strategy 11.4 Equal and Unequal Disposition

12 Profile II: Scope and Verification

12.1 All-Around, All-Over, and Limited Scope 12.2 Composite Profile and Coplanarity 12.3 Castings, Weldments, Sheet Metal, and CMM Evaluation 12.4 Combined Controls and Profile as a Refinement

13 Runout Controls

13.1 Circular and Total Runout 13.2 Datum-Axis Simulation and Rotating Parts 13.3 Runout vs Position, Profile, and Form

14 Exam Strategy and Calculations

14.1 Virtual/Resultant Condition and Bonus Formulas 14.2 Datum Shift and Worst-Case Boundary Calculations 14.3 Functional Gaging and Verification 14.4 Test-Day Tactics, Common Traps, and Review

13.1 Circular and Total Runout

Key Takeaways Explain This Topic AI

Runout is a datum-related surface control evaluated by rotating the part about a datum axis; both circular and total runout require a datum reference that establishes that axis.

Circular runout limits full indicator movement at each circular element independently; on a cylinder it combines local roundness and coaxial relationship but does not control variation along the length.

Total runout controls the entire indicated surface during rotation and sweep; on a cylinder it adds control of longitudinal form, while on a face it controls the entire face relative to the datum axis.

Runout can validly apply to a face perpendicular to a datum axis; the tolerance-zone geometry depends on whether the controlled surface surrounds the axis or intersects it.

Y14.5-2009 calls two or more datum features acting together multiple datum features; examples in this guide identify two journals as jointly establishing datum A instead of using a two-letter datum-precedence sequence.

Last updated: August 2026

13.1 Circular and Total Runout

Quick Answer: Both runout controls require a datum axis. Circular runout limits full indicator movement at each circular element independently. Total runout evaluates the entire indicated surface while the part rotates and the indicator traverses the surface. Runout is not limited to cylinders and cones: it can also control a face perpendicular to the datum axis.

The Datum Axis Is Mandatory

Runout is evaluated relative to an axis established from the referenced datum feature or features. A reference that establishes only a plane is insufficient unless another referenced feature establishes the axis needed for rotation. The setup must simulate the specified datum system; simply spinning the part about a convenient machine axis does not satisfy the drawing.

Circular Runout

For a cylindrical surface, circular runout is checked at each cross-section normal to the datum axis. The indicator remains at one axial location while the part makes a full revolution; full indicator movement at that circular element may not exceed the tolerance. Each section is evaluated independently, so circular runout does not control taper, bow, or other longitudinal variation between sections.

For a face perpendicular to the datum axis, circular runout may be checked along individual circular elements on the face. It limits face wobble at each selected radius during rotation. This is a valid face application, not an invalid callout.

Worked Cylinder Example

A shaft has two separated bearing journals identified as the multiple datum features that jointly establish datum A. A middle diameter has 0.05 circular runout to A. Both journals are simulated together to establish one datum axis, and the middle diameter is checked at several axial stations. A taper may pass if every station separately stays within 0.05; circular runout does not relate the readings along the length.

Total Runout

Total runout evaluates the entire controlled surface as the part rotates and the indicator traverses that surface. On a cylindrical surface, the tolerance zone is two coaxial cylinders separated by the tolerance value. It combines the coaxial relationship with circular and longitudinal surface variation, so taper or barrel shape that circular runout misses can fail total runout.

On a face perpendicular to the datum axis, the total-runout zone is two parallel planes perpendicular to that axis. Sweeping the indicator radially while the part rotates controls the entire face's variation relative to the datum axis, combining face flatness effects and perpendicular orientation in one requirement.

Comparison

• Aspect Circular Runout Total Runout
• Evaluation One circular element at a time Entire controlled surface during rotation and traverse

Cylinder Local roundness plus relationship to datum axis Adds longitudinal form, including taper and generator variation

• Face Wobble at each circular element Variation across the entire face
• Datum axis Required Required
• Same-value relationship Less comprehensive At least as restrictive for the corresponding surface application
• What Runout Does Not Do

Runout does not independently report how much error comes from form versus coaxiality or orientation; it limits their combined indicator effect. It does not replace position when the design intent is to locate a derived axis for assembly, and it does not apply to an arbitrary nonrotational contour such as a keyway wall. Select the control from the functional requirement and the surface being indicated.