Engineering Design Principles with Geometric Dimensioning …€¦ · PPT file · Web view · 2017-10-26Title: Engineering Design Principles with Geometric Dimensioning and Tolerancing

GD&T Location Table of ContentsReturn to the Previous Slide Slide 1 QuitMaster Table of ContentsGlossary

.490 - .500

C

A

B

.014 A B C

Tolerance of Position -- RFSTolerance of Position -- RFS

The information in the feature control The information in the feature control frame would be read as follows: frame would be read as follows: “Regardless of feature size, this feature “Regardless of feature size, this feature must be located on true position within must be located on true position within a cylindrical tolerance zone of .014 in. a cylindrical tolerance zone of .014 in. on diameter, with reference to datums on diameter, with reference to datums A (primary), B(secondary), and C A (primary), B(secondary), and C (tertiary).”(tertiary).”

Irrespective of how large or small the Irrespective of how large or small the actualactual hole size is—within its size hole size is—within its size limits—no additional tolerances are limits—no additional tolerances are available for the available for the locationlocation of the feature. of the feature. I’ll demonstrate in the next few slides. I’ll demonstrate in the next few slides.


True PositionTrue Position

Tolerance of Position -- RFSTolerance of Position -- RFSThe exact location of the hole is established with basic dimensions.The exact location of the hole is established with basic dimensions.




Location Tolerance Location Tolerance Zone –RFS Zone –RFS

The cylindrical tolerance zone is established in the feature control frame –(The cylindrical tolerance zone is established in the feature control frame –( .014). .014).

.014 A B C





.014 A B CFor the worst possible condition,For the worst possible condition,the hole axis is located at the the hole axis is located at the extreme limit of the cylindrical extreme limit of the cylindrical tolerance zone.tolerance zone.




Location Tolerance Location Tolerance Zone –RFS Zone –RFS (Always the Same)(Always the Same)

.014 A B C

MMC DiameterMMC Diameter

When the axis is located at the When the axis is located at the extreme limit of the tolerance extreme limit of the tolerance zone, the MMC holezone, the MMC hole axis would axis would be offset from the true position be offset from the true position by a distance equal to one-half by a distance equal to one-half of the position tolerance (.007). of the position tolerance (.007).





.014 A B C


The actual hole size may The actual hole size may vary between MMC vary between MMC (smallest diameter) and (smallest diameter) and LMC (largest diameter), LMC (largest diameter), but the but the axis locationaxis location cannot cannot violate the boundaries of violate the boundaries of its location tolerance.its location tolerance.

LMC DiameterLMC Diameter




Location Tolerance Location Tolerance Zone –RFSZone –RFS(Always the Same)(Always the Same)

.014 A B C



The white circle represents The white circle represents the MMC boundary. Its the MMC boundary. Its center is located at true center is located at true position. No element of the position. No element of the hole surface can be hole surface can be inside inside this boundary.this boundary.

MMC Boundary(VC Functional Gauge)





.014 A B C



The outer white circle The outer white circle represents the LMC represents the LMC boundary centered on boundary centered on true position. No true position. No elements on the surface elements on the surface of the hole can be of the hole can be outsideoutside of this of this boundary. The boundary. The following series of following series of slides will sequence the slides will sequence the progressive position of progressive position of the center of the hole as the center of the hole as it moves around the it moves around the tolerance zone.tolerance zone.

LMC BoundaryLMC Boundary






.014 A B C



The outer white circle The outer white circle represents the LMC represents the LMC boundary. No elements boundary. No elements on the surface of the on the surface of the hole can be hole can be outsideoutside of of this boundary. The this boundary. The following series of following series of slides will sequence the slides will sequence the progressive position of progressive position of the center of the hole as the center of the hole as it moves around the it moves around the tolerance zone.tolerance zone.







.014 A B C










.014 A B C










.014 A B C










.014 A B C










.014 A B C










.014 A B C










.014 A B C







TOLERANCE OF POSITION ATTOLERANCE OF POSITION ATMAXIMUM MATERIAL CONDITIONMAXIMUM MATERIAL CONDITION


The next example will illustrate the concept of bonus tolerance, in connection The next example will illustrate the concept of bonus tolerance, in connection with position tolerances. We will use the same drawing example that was used to with position tolerances. We will use the same drawing example that was used to discuss tolerances of position, when applied regardless of feature size (RFS). discuss tolerances of position, when applied regardless of feature size (RFS). One One of the significant differences you will see is the advantages of defining the of the significant differences you will see is the advantages of defining the tolerance zone for the axis of a hole as we did before—but this time, we will add tolerance zone for the axis of a hole as we did before—but this time, we will add the modifier for maximum material condition (MMC) to the tolerance the modifier for maximum material condition (MMC) to the tolerance specification in the feature control framespecification in the feature control frame. . Notice the changes that occur in Notice the changes that occur in location tolerances when modifiers are used, and as departure from MMC occurs.location tolerances when modifiers are used, and as departure from MMC occurs.

Tolerance of Position -- MMCTolerance of Position -- MMC


M

.490 - .500

.014 A B CC

A

B


The information in the feature The information in the feature control frame would be read as control frame would be read as follows: follows: “This feature must be “This feature must be located on true position within a located on true position within a cylindrical tolerance zone of .014 on cylindrical tolerance zone of .014 on diameter with reference to datums A diameter with reference to datums A (primary), B (secondary), and C (primary), B (secondary), and C (tertiary), when the hole is at its (tertiary), when the hole is at its smallest size, or MMC.”smallest size, or MMC.”

As the actual hole size increases in As the actual hole size increases in size from MMC, additional size from MMC, additional tolerance (equal to the amount of tolerance (equal to the amount of departure) may be departure) may be addedadded to the to the location tolerance for the feature.location tolerance for the feature.




The exact location of the hole is The exact location of the hole is established by basic dimensions.established by basic dimensions.



MMC Diameter (AxisMMC Diameter (Axisat Maximum Offset)at Maximum Offset)


The maximum material condition The maximum material condition diameter of .490 is shown at its diameter of .490 is shown at its maximum offset from true positionmaximum offset from true position—one-half the specified location —one-half the specified location tolerance.tolerance.



MMC DiameterMMC DiameterTolerance of Position -- MMCTolerance of Position -- MMC

As the size of the hole changes As the size of the hole changes within its tolerance range from within its tolerance range from MMC—smallest hole size MMC—smallest hole size limit, and increases in size limit, and increases in size towards the LMC, or upper towards the LMC, or upper size limit, an equal amount of size limit, an equal amount of tolerance can be tolerance can be addedadded to the to the axis axis locationlocation tolerance. tolerance.

Location Tolerance Location Tolerance Zone at LMCZone at LMC





The additional tolerance for The additional tolerance for the hole axis location (which is the hole axis location (which is equal to the amount of equal to the amount of departure from MMC), is departure from MMC), is called called “bonus tolerance.”“bonus tolerance.”

LMCLMCDiameterDiameter

Bonus Tolerance






When the hole size is at its When the hole size is at its lower limit (MMC), and lower limit (MMC), and positioned at the extreme positioned at the extreme limit of the MMC location limit of the MMC location tolerance, the MMC tolerance, the MMC boundary is established. boundary is established. When the feature of size is at When the feature of size is at this limit, no elements of the this limit, no elements of the hole hole surfacesurface may be inside may be inside this theoretical boundary. this theoretical boundary. This is the virtual condition This is the virtual condition of the hole, which also of the hole, which also simulates the mating part at simulates the mating part at its maximum material its maximum material conditioncondition..

MMC BoundaryMMC Boundary






MMC BoundaryMMC Boundary

When the hole size is at its When the hole size is at its upper limit (LMC), and upper limit (LMC), and positioned at the extreme positioned at the extreme limit of the location limit of the location tolerance, the LMC tolerance, the LMC boundary is boundary is established. established. No elements of No elements of the hole surfacethe hole surfacecan be out-side can be out-side this boundary.this boundary.







MMC BoundaryMMC Boundary(VC=MMC-Tol)(VC=MMC-Tol)


In this next series of slides, note In this next series of slides, note that while the size and location that while the size and location of the actual hole may vary, the of the actual hole may vary, the elements on elements on the surface of the holes the surface of the holes never violate their never violate their boundaries. This boundaries. This series will help series will help you to understand you to understand how the hole size how the hole size changes can affect changes can affect the location of the the location of the center axis—and its orientation.center axis—and its orientation.


Location Tolerance Location Tolerance at MMCat MMC

Location Tolerance at LMCLocation Tolerance at LMC







Axis location variance Axis location variance possibilities when position possibilities when position tolerance is modified to tolerance is modified to MMC.MMC.















































































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Engineering Design Principles with Geometric Dimensioning …€¦ · PPT file · Web view · 2017-10-26Title: Engineering Design Principles with Geometric Dimensioning and Tolerancing