What are some best practices and standards for runout control with GD&T?

Runout control is a crucial aspect of geometric dimensioning and tolerancing (GD&T), a system of symbols and rules for defining and communicating engineering design specifications. Runout control ensures that the rotational or linear movement of a part or feature does not deviate from its intended path or axis. In this article, you will learn about some best practices and standards for runout control with GD&T, including the types, symbols, modifiers, and tolerances of runout.

1 Types of runout

There are two types of runout in GD&T: axial runout and radial runout. Axial runout is the variation of a surface or a feature along its axis of rotation, such as the wobble of a wheel or a disk. Radial runout is the variation of a surface or a feature perpendicular to its axis of rotation, such as the eccentricity of a cylinder or a hole. Both types of runout can affect the performance, quality, and safety of a part or a system.

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Kiran Kumar

DMU SPOC Project Specialist I Digital Product Validation | CAD Functional Validator | ASME Certified GD&T Specialist I Design & Development Specialist I Automation & Efficiency Enthusiast I EX-DICV I EX-HAL
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We can also call these runouts as circular Runout and Total runout. Circular runout : 2D tolerance zone Total runout: 3D tolerance zone

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2 Symbols of runout

The symbols of runout in GD&T are the circular runout symbol and the total runout symbol. The circular runout symbol is a circle with a single slash, and it indicates that the runout is measured at a single circular cross-section of the part or feature. The total runout symbol is a circle with two slashes, and it indicates that the runout is measured along the entire length or surface of the part or feature. The runout symbols are placed in a feature control frame, which specifies the tolerance value, the datum reference, and any modifiers.

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3 Modifiers of runout

The modifiers of runout in GD&T are the free state modifier and the RFS modifier. The free state modifier is a symbol that looks like a circle with two crossed arrows, and it indicates that the part or feature is not restrained or clamped during the inspection. The free state modifier is used when the part or feature is flexible or deformable, and it allows for some variation in the runout due to the natural shape of the part or feature. The RFS modifier stands for regardless of feature size, and it indicates that the runout tolerance applies to the actual size of the part or feature, not the nominal size. The RFS modifier is used when the part or feature has a size tolerance, and it ensures that the runout tolerance is not affected by the size variation.

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4 Tolerances of runout

The tolerances of runout in GD&T are the values that specify the allowable deviation from the ideal path or axis of the part or feature. The tolerances of runout are expressed as a diameter value, which represents the maximum distance between two concentric circles that enclose the actual surface or feature. The tolerances of runout are determined by the design requirements, the manufacturing process, and the inspection method. The tolerances of runout are typically smaller than the tolerances of other geometric characteristics, such as flatness, roundness, or parallelism.

Runout control with GD&T is a powerful tool for ensuring the accuracy and functionality of rotating or linear parts or features. By following some best practices and standards for runout control with GD&T, you can improve the quality and reliability of your engineering design and production.

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Wahyudin P. Syam

Technical project manager | Content creator
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The main GD&T standard is ASM Y14.5. The simples way for verifying a run out tolerance is by using a universal CMM machine. However, the basic way of verifying tolerance run out is by using a dial gauges set ups for example, if we want to verify the simple circular run out of a tolerance, we can put the cylinder on a spindle. we then set the dial gauge tip of the cylinder surface where we want to check the circular runout and set zero. then, we rotate the cylinder and observed that dial should be not move more than the run out tolerance during a full rotation.

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5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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What are some best practices and standards for runout control with GD&T?

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1 Types of runout

2 Symbols of runout

3 Modifiers of runout

4 Tolerances of runout

5 Here’s what else to consider

Geometric Dimensioning & Tolerancing

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