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## CLASS DETAILS

- Class Name:
- Intro to GD&T 200 (1994)
- Description:
- This class introduces the fundamental concepts of geometric dimensioning and tolerancing (GD&T) and describes the main types of tolerances included in the standard. This class references the 1994 standard.
**Includes an Interactive Lab.** - Version:
- 1.0
- Difficulty:
- Intermediate
- Number of Lessons:
- 20
- Additional Language:
- Spanish, Chinese

## Class Outline

- Objectives
- What Is GD&T?
- Background of GD&T
- Datums and Features
- GD&T vs. Coordinate Tolerancing
- The Datum Reference Frame
- The Order of Datums
- Types of Tolerances
- Straightness and Flatness
- Circularity and Cylindricity
- Profile of a Line and Surface
- Angularity, Perpendicularity, and Parallelism
- Position
- Concentricity and Symmetry
- Circular and Total Runout
- Material Condition Modifiers
- Bonus Tolerance
- The Feature Control Frame
- Advantages of GD&T
- Summary

## Objectives

- Define GD&T.
- Describe the scope of GD&T standards.
- Distinguish between a datum and a feature.
- Distinguish between traditional tolerancing and GD&T.
- Define the datum reference frame.
- Describe how the datum reference frame and the part are related.
- List the major categories of geometric tolerances.
- Describe the straightness tolerance.
- Describe the flatness tolerance.
- Describe the circularity tolerance.
- Describe the cylindricity tolerance.
- Describe the profile of a line tolerance.
- Describe the profile of a surface tolerance.
- Describe the angularity tolerance.
- Describe the perpendicularity tolerance.
- Describe the parallelism tolerance.
- Describe the position tolerance.
- Describe the concentricity tolerance.
- Describe the symmetry tolerance.
- Describe the circular runout tolerance.
- Describe the total runout tolerance.
- List the material condition modifiers.
- Describe how bonus tolerance is applied to a hole.
- List the contents of the feature control frame.
- Describe the advantages of GD&T.

## Job Roles

## Certifications

SME- CMfgT

- CNC Lathe Operations
- CNC Milling Operations
- Drill Press I
- Grinding I
- Job Planning, Benchwork, & Layout I
- Metalforming I
- Turning Operations: Turning Chucking Skills

- MSSC Quality Practices and Measurement

## Glossary

Vocabulary Term | Definition |
---|---|

angle plate | A precise measurement device used to establish an accurate 90° vertical surface. |

angularity | A three-dimensional geometric tolerance that controls how much a surface, axis, or plane can deviate from the angle described in the design specifications. |

ASME | The American Society of Mechanical Engineers. ASME is an organization that publishes technical materials and sets industrial and manufacturing standards. |

bonus tolerance | Additional tolerance that applies to a feature as its size shifts from a stated material condition. Both MMC and LMC allow bonus tolerance. |

circular runout | A two-dimensional geometric tolerance that controls the form, orientation, and location of multiple cross sections of a cylindrical part as it rotates. |

circularity | A two-dimensional geometric tolerance that controls how much a feature can deviate from a perfect circle. |

concentric | Sharing the same center. |

concentricity | A three-dimensional geometric tolerance that controls how much the median points of multiple diameters may deviate from the specified datum axis. |

coordinate tolerancing | A system for describing the design of a part that compares its features to distances along three linear axes. These axes create an imaginary rectangular grid. |

cross section | A section of a feature that is formed by an intersecting imaginary plane. |

cylindricity | A three-dimensional geometric tolerance that controls how much a feature can deviate from a perfect cylinder. |

datum | An imaginary, perfect geometric shape or form. A perfect point, line, flat plane, circle, or cylinder are all examples of possible datums. |

datum feature | A physical feature that acts as an acceptable substitute for a datum. Datum features relate the various features of the part to each other. |

datum reference frame | Three imaginary planes perpendicular to one another that are mapped onto the part to relate features to each other. |

feature | A physical feature of a part that naturally contains variation and imperfections. A corner, edge, flat surface, or hole are all examples of possible features. |

feature control frame | A series of compartments containing symbols and values that describe the tolerance of a feature. The order and purpose of these compartments follow a consistent standard. |

fixture | A dedicated workholding device used to locate and hold a part during machining or inspection. |

flatness | A three-dimensional geometric tolerance that controls how much a feature can deviate from a flat plane. |

form tolerance | A group of geometric tolerances that limit the amount of error in the shape of a feature. Form tolerances are independent tolerances. |

functional gage | A gage for a specific part that quickly checks its form and fit in a manner similar to its intended use. |

geometric dimensioning and tolerancing | An international standard for communicating instructions about the design and manufacturing of parts. GD&T uses universal symbols and emphasizes the function of the part. |

granite surface plate | A precise, flat plate made of granite that is used to establish a datum plane for inspection. Granite surface plates are available in standardized grades. |

individual tolerance | A tolerance that does not require a specified datum. |

ISO | The International Organization for Standardization. ISO is an organization based in Switzerland that develops and publishes standards for its international membership base. |

least material condition | The point at which a feature contains the least amount of material within its acceptable size limit. The largest acceptable hole and the smallest acceptable shaft are examples of LMC. |

location tolerance | A group of geometric tolerances that limit the location or placement of features. Location tolerances are related tolerances. |

material condition modifier | One of three modifiers that further define the tolerance of a feature in relation to its acceptable size limits. |

maximum material condition | The point at which a feature contains the greatest amount of material within its acceptable size limit. The smallest acceptable hole and the largest acceptable shaft are examples of MMC. |

median point | A point that is exactly the same distance between two outer points. |

orientation tolerance | A group of geometric tolerances that limit the direction, or orientation, of a feature in relation to other features. Orientation tolerances are related tolerances. |

parallelism | A three-dimensional geometric tolerance that controls how much a surface, axis, or plane can deviate from an orientation parallel to the specified datum. |

perpendicularity | A three-dimensional geometric tolerance that controls how much a surface, axis, or plane can deviate from a 90 degree angle. |

position | A three-dimensional geometric tolerance that controls how much the location of a feature can deviate from its true position. |

primary datum | The datum feature that first situates the part within the datum reference frame. The primary datum is the first feature to contact a fixture or surface during assembly. |

profile | The outline of a part feature within a given plane. |

profile of a line | A two-dimensional geometric tolerance that controls how much the outline of a feature can deviate from the true profile. |

profile of a surface | A three-dimensional geometric tolerance that controls how much a surface can deviate from the true profile. |

profile tolerance | A group of powerful geometric tolerances that control the size, location, orientation, and form of a feature. Profile tolerances can be either independent or related. |

regardless of feature size | A modifier indicating that the stated tolerance for a feature applies regardless of its actual size within an acceptable size limit. RFS does not permit bonus tolerance. |

related tolerance | A tolerance that requires a specified datum. |

roundness measuring machine | A sophisticated inspection device with a precision spindle that measures various circular or cylindrical features. |

runout tolerance | A group of geometric tolerances that simultaneously limit the form, location, and orientation of cylindrical parts. Runout tolerances are related tolerances requiring a datum axis. |

secondary datum | The datum feature that situates the part within the datum reference frame after the primary datum. The secondary datum is the second feature to contact a fixture or surface during assembly. |

straightness | A two-dimensional geometric tolerance that controls how much a feature can deviate from a straight line. |

symmetry | A three-dimensional geometric tolerance that controls how much the median points between two features may deviate from a specified axis or center plane. |

tertiary datum | The datum feature that situates the part within the datum reference frame after the secondary datum. |

three-dimensional tolerance | A tolerance that controls a shape having a length, width, and depth. |

tolerance | An unwanted but acceptable deviation from a given dimension. Tolerances indicate the allowable difference between a physical feature and its intended design. |

tolerance zone | An imaginary zone in which a part feature must be completely contained for the part to pass inspection. |

total runout | A three-dimensional geometric tolerance that controls the form, orientation, and location of the entire length of a cylindrical part as it rotates. |

true position | The imaginary perfect position of a feature described by the design specifications. |

true profile | The perfect, imaginary profile described by the design specifications. |

two-dimensional tolerance | A tolerance that controls a shape having only a length and width. |