Geometric Dimensioning and Tolerancing

DIMENSIONAL ENGINEERING Based on the ASME Y14.5M1994 Dimensioning and Tolerancing Standard

INTRODUCTION Geometric dimensioning and tolerancing (GD&T) is an international engineering language that is used on engineering drawings (blue prints) to describe product in three dimensions. GD&T uses a series of internationally recognized symbols rather than words to describe the product. These symbols are applied to the features of a part and provide a very concise and clear definition of design intent. GD&T is a very precise mathematical language that describes the form, orientation and location of part features in zones of tolerance. These zones of tolerance are then described relative to a Cartesian coordinate system. ASME Y14.5M-1994 American national Standards Institute/American Society of Mechanical Engineers

Tolerances of Form

Straightness (ASME Y14.5M-1994, 6.4.1)

Flatness (ASME Y14.5M-1994, 6.4.2)

Circularity (ASME Y14.5M-1994, 6.4.3)

Cylindricity (ASME Y14.5M-1994, 6.4.4)

Extreme Variations of Form Allowed By Size Tolerance 25.1 25

25 (MMC)

25.1 (LMC)

25.1 (LMC)

25 (MMC)

MMC Perfect Form Boundary

25.1 (LMC)

Internal Feature of Size

Extreme Variations of Form Allowed By Size Tolerance 25 24.9

24.9 (LMC)

25 (MMC)

24.9 (LMC)

MMC Perfect Form Boundary

25 (MMC)

24.9 (LMC)

External Feature of Size

Straightness (Flat Surfaces) 0.5

0.1

25 +/-0.25

0.1 Tolerance 0.5 Tolerance

Straightness is the condition where an element of a surface or an axis is a straight line

Straightness (Flat Surfaces) 0.5 Tolerance Zone

25.25 max 24.75 min

0.1 Tolerance Zone

In this example each line element of the surface must lie within a tolerance zone defined by two parallel lines separated by the specified tolerance value applied to each view. All points on the surface must lie within the limits of size and the applicable straightness limit.

The straightness tolerance is applied in the view where the elements to be controlled are represented by a straight line

Straightness (Surface Elements) 0.1

0.1 Tolerance Zone MMC

0.1 Tolerance Zone MMC

0.1 Tolerance Zone MMC

In this example each longitudinal element of the surface must lie within a tolerance zone defined by two parallel lines separated by the specified tolerance value. The feature must be within the limits of size and the boundary of perfect form at MMC. Any barreling or waisting of the feature must not exceed the size limits of the feature.

Straightness (RFS) 0.1

0.1 Diameter Tolerance Zone MMC

Outer Boundary (Max)

Outer Boundary = Actual Feature Size + Straightness Tolerance

In this example the derived median line of the feature’s actual local size must lie within a tolerance zone defined by a cylinder whose diameter is equal to the specified tolerance value regardless of the feature size. Each circular element of the feature must be within the specified limits of size. However, the boundary of perfect form at MMC can be violated up to the maximum outer boundary or virtual condition diameter.

Straightness (MMC) 15 14.85 0.1

15 (MMC)

M

0.1 Diameter Tolerance Zone

15.1 Virtual Condition 14.85 (LMC)

0.25 Diameter Tolerance Zone

15.1 Virtual Condition Virtual Condition = MMC Feature Size + Straightness Tolerance

In this example the derived median line of the feature’s actual local size must lie within a tolerance zone defined by a cylinder whose diameter is equal to the specified tolerance value at MMC. As each circular element of the feature departs from MMC, the diameter of the tolerance cylinder is allowed to increase by an amount equal to the departure from the local MMC size. Each circular element of the feature must be within the specified limits of size. However, the boundary of perfect form at MMC can be violated up to the virtual condition diameter.

Flatness 0.1

25 +/-0.25

0.1 Tolerance Zone 0.1 Tolerance Zone

24.75 min

25.25 max

In this example the entire surface must lie within a tolerance zone defined by two parallel planes separated by the specified tolerance value. All points on the surface must lie within the limits of size and the flatness limit.

Flatness is the condition of a surface having all elements in one plane. Flatness must fall within the limits of size. The flatness tolerance must be less than the size tolerance.

Circularity (Roundness) 0.1

90 0.1 90

0.1 Wide Tolerance Zone

In this example each circular element of the surface must lie within a tolerance zone defined by two concentric circles separated by the specified tolerance value. All points on the surface must lie within the limits of size and the circularity limit.

Circularity is the condition of a surface where all points of the surface intersected by any plane perpendicular to a common axis are equidistant from that axis. The circularity tolerance must be less than the size tolerance

Cylindricity 0.1

0.1 Tolerance Zone

MMC

In this example the entire surface must lie within a tolerance zone defined by two concentric cylinders separated by the specified tolerance value. All points on the surface must lie within the limits of size and the cylindricity limit.

Cylindricity is the condition of a surface of revolution in which all points are equidistant from a common axis. Cylindricity is a composite control of form which includes circularity (roundness), straightness, and taper of a cylindrical feature.

Form Control Quiz Questions #1-5 Fill in blanks (choose from below)

1. The four form controls are ____________, ________, ___________, and ____________. 2. Rule #1 states that unless otherwise specified a feature of size must have ____________at MMC.

3. ____________ and ___________ are individual line or circular element (2-D) controls.

4. ________ and ____________are surface (3-D) controls. 5. Circularity can be applied to both ________and _______ cylindrical parts.

straightness straight perfect form

cylindricity angularity flatness tapered profile circularity true position

Answer questions #6-10 True or False

6. Form controls require a datum reference. 7. Form controls do not directly control a feature’s size. 8. A feature’s form tolerance must be less than it’s size tolerance.

9. Flatness controls the orientation of a feature. 10. Size limits implicitly control a feature’s form.

Tolerances of Orientation Angularity (ASME Y14.5M-1994 ,6.6.2)

Perpendicularity (ASME Y14.5M-1994 ,6.6.4)

Parallelism (ASME Y14.5M-1994 ,6.6.3)

Angularity (Feature Surface to Datum Surface) 20 +/-0.5 0.3 A 30

o

A 19.5 min

20.5 max

30

A

0.3 Wide Tolerance Zone

o

30

A

0.3 Wide Tolerance Zone

The tolerance zone in this example is defined by two parallel planes oriented at the specified angle to the datum reference plane.

Angularity is the condition of the planar feature surface at a specified angle (other than 90 degrees) to the datum reference plane, within the specified tolerance zone.

o

Angularity (Feature Axis to Datum Surface) NOTE: Tolerance applies to feature at RFS 0.3 A

0.3 Circular Tolerance Zone

0.3 Circular Tolerance Zone

60 o

A

The tolerance zone in this example is defined by a cylinder equal to the length of the feature, oriented at the specified angle to the datum reference plane.

A

Angularity is the condition of the feature axis at a specified angle (other than 90 degrees) to the datum reference plane, within the specified tolerance zone.

Angularity (Feature Axis to Datum Axis) NOTE: Feature axis must lie within tolerance zone cylinder 0.3 A

NOTE: Tolerance applies to feature at RFS

A

0.3 Circular Tolerance Zone

0.3 Circular Tolerance Zone

45 o

Datum Axis A The tolerance zone in this example is defined by a cylinder equal to the length of the feature, oriented at the specified angle to the datum reference axis.

Angularity is the condition of the feature axis at a specified angle (other than 90 degrees) to the datum reference axis, within the specified tolerance zone.

Perpendicularity (Feature Surface to Datum Surface) 0.3 A

A 0.3 Wide Tolerance Zone

A

0.3 Wide Tolerance Zone

The tolerance zone in this example is defined by two parallel planes oriented perpendicular to the datum reference plane.

A

Perpendicularity is the condition of the planar feature surface at a right angle to the datum reference plane, within the specified tolerance zone.

Perpendicularity (Feature Axis to Datum Surface) 0.3 Diameter Tolerance Zone

NOTE: Tolerance applies to feature at RFS 0.3 Circular Tolerance Zone

C 0.3 Circular Tolerance Zone 0.3 C

The tolerance zone in this example is defined by a cylinder equal to the length of the feature, oriented perpendicular to the datum reference plane.

Perpendicularity is the condition of the feature axis at a right angle to the datum reference plane, within the specified tolerance zone.

Perpendicularity (Feature Axis to Datum Axis) NOTE: Tolerance applies to feature at RFS 0.3 A

A

0.3 Wide Tolerance Zone

Datum Axis A The tolerance zone in this example is defined by two parallel planes oriented perpendicular to the datum reference axis.

Perpendicularity is the condition of the feature axis at a right angle to the datum reference axis, within the specified tolerance zone.

Parallelism (Feature Surface to Datum Surface)

0.3 A

25 +/-0.5

A 0.3 Wide Tolerance Zone

25.5 max

0.3 Wide Tolerance Zone

24.5 min

A

The tolerance zone in this example is defined by two parallel planes oriented parallel to the datum reference plane.

A

Parallelism is the condition of the planar feature surface equidistant at all points from the datum reference plane, within the specified tolerance zone.

Parallelism (Feature Axis to Datum Surface) NOTE: The specified tolerance does not apply to the orientation of the feature axis in this direction

NOTE: Tolerance applies to feature at RFS

0.3 Wide Tolerance Zone

0.3 A

A

The tolerance zone in this example is defined by two parallel planes oriented parallel to the datum reference plane.

A

Parallelism is the condition of the feature axis equidistant along its length from the datum reference plane, within the specified tolerance zone.

Parallelism (Feature Axis to Datum Surfaces) 0.3 Circular Tolerance Zone

B

NOTE: Tolerance applies to feature at RFS 0.3 Circular Tolerance Zone

0.3 Circular Tolerance Zone 0.3 A B

B

A

The tolerance zone in this example is defined by a cylinder equal to the length of the feature, oriented parallel to the datum reference planes.

A

Parallelism is the condition of the feature axis equidistant along its length from the two datum reference planes, within the specified tolerance zone.

Parallelism (Feature Axis to Datum Axis) The tolerance zone in this example is defined by a cylinder equal to the length of the feature, oriented parallel to the datum reference axis. NOTE: Tolerance applies to feature at RFS 0.1 Circular Tolerance Zone

0.1 A

A

0.1 Circular Tolerance Zone

Datum Axis A

Parallelism is the condition of the feature axis equidistant along its length from the datum reference axis, within the specified tolerance zone.

Orientation Control Quiz Questions #1-5 Fill in blanks (choose from below)

1. The three orientation controls are __________, ___________, and ________________. 2. A _______________

is always required when applying any of

the orientation controls.

3. ________________

is the appropriate geometric tolerance when controlling the orientation of a feature at right angles to a datum reference.

4. Mathematically all three orientation tolerances are _________. 5. Orientation tolerances do not control the ________ of a feature. perpendicularity datum feature angularity

datum target location identical

datum reference parallelism profile

Answer questions #6-10 True or False

6. Orientation tolerances indirectly control a feature’s form. 7. Orientation tolerance zones can be cylindrical. 8. To apply a perpendicularity tolerance the desired angle must be indicated as a basic dimension.

9. Parallelism tolerances do not apply to features of size. 10. To apply an angularity tolerance the desired angle must be indicated as a basic dimension.

Tolerances of Runout Circular Runout (ASME Y14.5M-1994, 6.7.1.2.1)

Total Runout (ASME Y14.5M-1994 ,6.7.1.2.2)

Features Applicable to Runout Tolerancing Internal surfaces constructed around a datum axis

External surfaces constructed around a datum axis Datum axis (established from datum feature

Datum feature

Angled surfaces constructed around a datum axis

Surfaces constructed perpendicular to a datum axis

Circular Runout Total Tolerance

Maximum

Circular runout can only be applied on an RFS basis and cannot be modified to MMC or LMC.

Minimum

Full Indicator Movement Maximum Reading

+

Minimum Reading 0

-

Measuring position #1 (circular element #1)

Full Part Rotation

Measuring position #2 (circular element #2)

When measuring circular runout, the indicator must be reset to zero at each measuring position along the feature surface. Each individual circular element of the surface is independently allowed the full specified tolerance. In this example, circular runout can be used to detect 2dimensional wobble (orientation) and waviness (form), but not 3-dimensional characteristics such as surface profile (overall form) or surface wobble (overall orientation).

Circular Runout (Angled Surface to Datum Axis) 0.75 A A

50 +/-0.25

50

o

+/- 2

o

As Shown on Drawing Means This: Allowable indicator reading = 0.75 max. Full Indicator Movement

(

) -

0

+

The tolerance zone for any individual circular element is equal to the total allowable movement of a dial indicator fixed in a position normal to the true geometric shape of the feature surface when the part is rotated 360 degrees about the datum axis. The tolerance limit is applied independently to each individual measuring position along the feature surface. Collet or Chuck

When measuring circular runout, the indicator must be reset when repositioned along the feature surface.

Datum axis A

360 o Part Rotation

Single circular element

NOTE: Circular runout in this example only controls the 2-dimensional circular elements (circularity and coaxiality) of the angled feature surface not the entire angled feature surface

Circular Runout (Surface Perpendicular to Datum Axis) 0.75 A A

50 +/-0.25

As Shown on Drawing Means This:

Single circular element

The tolerance zone for any individual circular element is equal to the total allowable movement of a dial indicator fixed in a position normal to the true geometric shape of the feature surface when the part is rotated 360 degrees about the datum axis. The tolerance limit is applied independently to each individual measuring position along the feature surface. -

360 o Part Rotation

0

+

When measuring circular runout, the indicator must be reset when repositioned along the feature surface. Allowable indicator reading = 0.75 max.

Datum axis A NOTE: Circular runout in this example will only control variation in the 2-dimensional circular elements of the planar surface (wobble and waviness) not the entire feature surface

Circular Runout (Surface Coaxial to Datum Axis) 0.75 A

A

50 +/-0.25

As Shown on Drawing Means This:

The tolerance zone for any individual circular element is equal to the total allowable movement of a dial indicator fixed in a position normal to the true geometric shape of the feature surface when the part is rotated 360 degrees about the datum axis. The tolerance limit is applied independently to each individual measuring position along the feature surface. +

Allowable indicator reading = 0.75 max.

0

-

When measuring circular runout, the indicator must be reset when repositioned along the feature surface.

Single circular element 360 o Part Rotation

Datum axis A

NOTE: Circular runout in this example will only control variation in the 2-dimensional circular elements of the surface (circularity and coaxiality) not the entire feature surface

Circular Runout (Surface Coaxial to Datum Axis) 0.75 A-B

A

B

As Shown on Drawing Means This:

The tolerance zone for any individual circular element is equal to the total allowable movement of a dial indicator fixed in a position normal to the true geometric shape of the feature surface when the part is rotated 360 degrees about the datum axis. The tolerance limit is applied independently to each individual measuring position along the feature surface. +

Allowable indicator reading = 0.75 max.

Machine center

0

-

When measuring circular runout, the indicator must be reset when repositioned along the feature surface.

Single circular element Datum axis A-B

360 o Part Rotation

Machine center NOTE: Circular runout in this example will only control variation in the 2-dimensional circular elements of the surface (circularity and coaxiality) not the entire feature surface

Circular Runout (Surface Related to Datum Surface and Axis) A

B

0.75 A B 50 +/-0.25

As Shown on Drawing The tolerance zone for any individual circular element is equal to the total allowable movement of a dial indicator fixed in a position normal to the true geometric shape of the feature surface when the part is located against the datum surface and rotated 360 degrees about the datum axis. The tolerance limit is applied independently to each individual measuring position along the feature surface.

Means This:

Single circular element Allowable indicator reading = 0.75 max.

Stop collar 360 o Part Rotation

+

0

-

Collet or Chuck

Datum axis B

When measuring circular runout, the indicator must be reset when repositioned along the feature surface.

Datum plane A

Total Runout Total Tolerance

Maximum

Total runout can only be applied on an RFS basis and cannot be modified to MMC or LMC.

Minimum

Full Indicator Movement Maximum Reading

Minimum Reading

+

0

-

Indicator Path

Full Part Rotation

+

0

-

When measuring total runout, the indicator is moved in a straight line along the feature surface while the part is rotated about the datum axis. It is also acceptable to measure total runout by evaluating an appropriate number of individual circular elements along the surface while the part is rotated about the datum axis. Because the tolerance value is applied to the entire surface, the indicator must not be reset to zero when moved to each measuring position. In this example, total runout can be used to measure surface profile (overall form) and surface wobble (overall orientation).

Total Runout (Angled Surface to Datum Axis) 0.75 A A

50 +/-0.25

50

o

+/- 2

o

As Shown on Drawing Means This: When measuring total runout, the indicator must not be reset when repositioned along the feature surface.

-

0

+

0

+

The tolerance zone for the entire angled surface is equal to the total allowable movement of a dial indicator positioned normal to the true geometric shape of the feature surface when the part is rotated about the datum axis and the indicator is moved along the entire length of the feature surface. Allowable indicator reading = 0.75 max. (applies to the entire feature surface)

Collet or Chuck

Full Part Rotation

Datum axis A

NOTE: Unlike circular runout, the use of total runout will provide 3-dimensional composite control of the cumulative variations of circularity, coaxiality, angularity, taper and profile of the angled surface

Total Runout (Surface Perpendicular to Datum Axis) 0.75 A 10 35 50 +/-0.25

A

Means This:

10 35 Full Part Rotation

As Shown on Drawing

The tolerance zone for the portion of the feature surface indicated is equal to the total allowable movement of a dial indicator positioned normal to the true geometric shape of the feature surface when the part is rotated about the datum axis and the indicator is moved along the portion of the feature surface within the area described by the basic dimensions.

-

0

-

0

+ +

When measuring total runout, the indicator must not be reset when repositioned along the feature surface.

Allowable indicator reading = 0.75 max. (applies to portion of feature surface indicated)

Datum axis A NOTE: The use of total runout in this example will provide composite control of the cumulative variations of perpendicularity (wobble) and flatness (concavity or convexity) of the feature surface.

Runout Control Quiz Answer questions #1-12 True or False

1. Total runout is a 2-dimensional

control.

2. Runout tolerances are used on rotating parts. 3. Circular runout tolerances apply to single elements . 4. Total runout tolerances should be applied at MMC. 5. Runout tolerances can be applied to surfaces at right angles to the datum reference.

6. Circular runout tolerances are used to control an entire feature surface.

7. Runout tolerances always require a datum reference. 8. Circular runout and total runout both control axis to surface relationships.

9. Circular runout can be applied to control taper of a part. 10. Total runout tolerances are an appropriate way to limit “wobble” of a rotating surface.

11.

Runout tolerances are used to control a feature’s size.

12. Total runout can control circularity, straightness, taper, coaxiality, angularity and any other surface variation.

Tolerances of Profile

Profile of a Line (ASME Y14.5M-1994, 6.5.2b)

Profile of a Surface (ASME Y14.5M-1994, 6.5.2a)

Profile of a Line 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

C

1 A B C

17 +/- 1 A

1 Wide Profile Tolerance Zone

2 Wide Size Tolerance Zone 18 Max 16 Min.

The profile tolerance zone in this example is defined by two parallel lines oriented with respect to the datum reference frame. The profile tolerance zone is free to float within the larger size tolerance and applies only to the form and orientation of any individual line element along the entire surface. Profile of a Line is a two-dimensional tolerance that can be applied to a part feature in situations where the control of the entire feature surface as a single entity is not required or desired. The tolerance applies to the line element of the surface at each individual cross section indicated on the drawing.

Profile of a Surface 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

2 A B C

C

23.5

A

2 Wide Tolerance Zone Size, Form and Orientation

23.5

Nominal Location

The profile tolerance zone in this example is defined by two parallel planes oriented with respect to the datum reference frame. The profile tolerance zone is located and aligned in a way that enables the part surface to vary equally about the true profile of the feature.

Profile of a Surface is a three-dimensional tolerance that can be applied to a part feature in situations where the control of the entire feature surface as a single entity is desired. The tolerance applies to the entire surface and can be used to control size, location, form and/or orientation of a feature surface.

Profile of a Surface (Bilateral Tolerance) 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

1 A B C

C 50

1 Wide Total Tolerance Zone

B

0.5 Inboard 0.5 Outboard

C

50

Nominal Location

The tolerance zone in this example is defined by two parallel planes oriented with respect to the datum reference frame. The profile tolerance zone is located and aligned in a way that enables the part surface to vary equally about the true profile of the trim. Profile of a Surface when applied to trim edges of sheet metal parts will control the location, form and orientation of the entire trimmed surface. When a bilateral value is specified, the tolerance zone allows the trim edge variation and/or locational error to be on both sides of the true profile. The tolerance applies to the entire edge surface.

Profile of a Surface (Unilateral Tolerance) 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

0.5 A B C

C 50

0.5 Wide Total Tolerance Zone

B

C

50

Nominal Location

The tolerance zone in this example is defined by two parallel planes oriented with respect to the datum reference frame. The profile tolerance zone is located and aligned in a way that allows the trim surface to vary from the true profile only in the inboard direction. Profile of a Surface when applied to trim edges of sheet metal parts will control the location, form and orientation of the entire trimmed surface. When a unilateral value is specified, the tolerance zone limits the trim edge variation and/or locational error to one side of the true profile. The tolerance applies to the entire edge surface.

Profile of a Surface (Unequal Bilateral Tolerance) 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

0.5 1.2 A B C C 50

1.2 Wide Total Tolerance Zone

B

0.5 Inboard 0.7 Outboard

C

50

Nominal Location

The tolerance zone in this example is defined by two parallel planes oriented with respect to the datum reference frame. The profile tolerance zone is located and aligned in a way that enables the part surface to vary from the true profile more in one direction (outboard) than in the other (inboard). Profile of a Surface when applied to trim edges of sheet metal parts will control the location, form and orientation of the entire trimmed surface. Typically when unequal values are specified, the tolerance zone will represent the actual measured trim edge variation and/or locational error. The tolerance applies to the entire edge surface.

Profile of a Surface

0.5 A 0.1

Location & Orientation Form Only

25

A 0.1 Wide Tolerance Zone 25.25

24.75

A

Composite Profile of Two Coplanar Surfaces w/o Orientation Refinement

Profile of a Surface 0.5 A 0.1 A

Location Form & Orientation

25

A 0.1 Wide Tolerance Zone 25.25

A

0.1 Wide Tolerance Zone

24.75

A

Composite Profile of Two Coplanar Surfaces With Orientation Refinement

Profile Control Quiz Answer questions #1-13 True or False

1. Profile tolerances always require a datum reference. 2. Profile of a surface tolerance is a 2-dimensional control. 3. Profile of a surface tolerance should be used to control trim edges on sheet metal parts.

4. Profile of a line tolerances should be applied at MMC. 5. Profile tolerances can be applied to features of size. 6. Profile tolerances can be combined with other geometric controls such as flatness to control a feature.

7. Profile of a line tolerances apply to an entire surface. 8. Profile of a line controls apply to individual line elements. 9. Profile tolerances only control the location of a surface. 10. Composite profile controls should be avoided because they are more restrictive and very difficult to check.

11.

Profile tolerances can be applied either bilateral or unilateral to a feature.

12. Profile tolerances can be applied in both freestate and restrained datum conditions.

13. Tolerances shown in the lower segment of a composite profile feature control frame control the location of a feature to the specified datums.

Profile Control Quiz Questions #1-9 Fill in blanks (choose from below)

1. The two types of profile tolerances are _________________, and ____________________. 2. Profile tolerances can be used to control the ________, ____, ___________ , and sometimes size of a feature. 3. Profile tolerances can be applied _________ or __________. 4. _________________ tolerances are 2-dimensional controls. 5. ____________________

tolerances are 3-dimensional controls.

6. _________________ can be used when different tolerances are required for location and form and/or orientation.

7. When using profile tolerances to control the location and/or orientation of a feature, a _______________ must be included in the feature control frame.

8. When using profile tolerances to control form only, a ______ __________ is not required in the feature control frame. 9. In composite profile applications, the tolerance shown in the upper segment of the feature control frame applies only to the ________ of the feature.

composite profile bilateral virtual condition profile of a surface primary datum orientation datum reference unilateral profile of a line location true geometric counterpart form

Tolerances of Location True Position (ASME Y14.5M-1994, 5.2)

Concentricity (ASME Y14.5M-1994, 5.12)

Symmetry (ASME Y14.5M-1994, 5.13)

Notes

Coordinate vs Geometric Tolerancing Methods 8.5 +/- 0.1 1.4 A B C

8.5 +/- 0.1

Circular Tolerance Zone

Rectangular Tolerance Zone 10.25 +/- 0.5

10.25 B

10.25 +/- 0.5

10.25

C

A

Coordinate Dimensioning

Geometric Dimensioning

+/- 0.5 1.4 +/- 0.5

Rectangular Tolerance Zone

57% Larger Tolerance Zone

Circular Tolerance Zone

Circular Tolerance Zone

Rectangular Tolerance Zone

Increased Effective Tolerance

Positional Tolerance Verification (Applies when a circular tolerance is indicated)

X Z Feature axis actual location (measured)

Y

Positional tolerance zone cylinder Actual feature boundary

Feature axis true position (designed)

Formula to determine the actual radial position of a feature using measured coordinate values (RFS) Z=

Z

X2 + Y2 positional tolerance /2

Z = total radial deviation X2 = “X” measured deviation Y2 = “Y” measured deviation

Positional Tolerance Verification (Applies when a circular tolerance is indicated)

X Z Feature axis actual location (measured)

Y

Positional tolerance zone cylinder Actual feature boundary

Feature axis true position (designed)

Formula to determine the actual radial position of a feature using measured coordinate values (MMC) X2 + Y2 +( actual - MMC) Z 2 = positional tolerance Z = total radial deviation X2 = “X” measured deviation Y2 = “Y” measured deviation Z =

Bi-directional True Position Rectangular Coordinate Method 1.5 A B C

2X

2X

0.5 A B C

C

A

10

B 10

As Shown on Drawing

35

2X

6 +/-0.25

Means This: True Position Related to Datum Reference Frame

1.5 Wide Tolerance Zone

C

10

B 10

35

0.5 Wide Tolerance Zone

Each axis must lie within the 1.5 X 0.5 rectangular tolerance zone basically located to the datum reference frame

Bi-directional True Position Multiple Single-Segment Method 2X

6 +/-0.25

1.5 A B C 0.5 A B

C

A

10

B 10

As Shown on Drawing

35

Means This: True Position Related to Datum Reference Frame

1.5 Wide Tolerance Zone

C

10

B 10

35

0.5 Wide Tolerance Zone

Each axis must lie within the 1.5 X 0.5 rectangular tolerance zone basically located to the datum reference frame

Bi-directional True Position Noncylndrical Features (Boundary Concept) 2X 13 +/-0.25 1.5 M A B C BOUNDARY

2X 6 +/-0.25 0.5 M A B C BOUNDARY

C

A

10

B 10

35

As Shown on Drawing

5.75 MMC length of slot -0.50 Position tolerance 5.25 maximum boundary

Means This: Both holes must be within the size limits and no portion of their surfaces may lie within the area described by the 11.25 x 5.25 maximum boundaries when the part is positioned with respect to the datum reference frame. The boundary concept can only be applied on an MMC basis.

12.75 MMC width of slot -1.50 Position tolerance 11.25 Maximum boundary

True position boundary related to datum reference frame

C 90 o 10 10

35

B

A

Composite True Position Without Pattern Orientation Control 2X

6 +/-0.25 1.5 A B C 0.5 A

C

A

10

B 10

35

As Shown on Drawing

Means This: 1.5 Pattern-Locating Tolerance Zone Cylinder

0.5 Feature-Relating Tolerance Zone Cylinder

pattern location relative to Datums A, B, and C

pattern orientation relative to Datum A only (perpendicularity)

C

10

B 10

35

True Position Related to Datum Reference Frame

Each axis must lie within each tolerance zone simultaneously

Composite True Position With Pattern Orientation Control 2X

6 +/-0.25 1.5 A B C 0.5 A B

C

A

10

B 10

35

As Shown on Drawing

Means This: 1.5 Pattern-Locating Tolerance Zone Cylinder

True Position Related to Datum Reference Frame

pattern location relative to Datums A, B, and C

C

10

B 10

35

0.5 Feature-Relating Tolerance Zone Cylinder pattern orientation relative to Datums A and B

Each axis must lie within each tolerance zone simultaneously

Location (Concentricity) Datum Features at RFS 6.35 +/- 0.05 0.5 A

A

15.95 15.90

As Shown on Drawing Means This:

Axis of Datum Feature A

0.5 Coaxial Tolerance Zone

Derived Median Points of Diametrically Opposed Elements Within the limits of size and regardless of feature size, all median points of diametrically opposed elements must lie within a 0.5 cylindrical tolerance zone. The axis of the tolerance zone coincides with the axis of datum feature A. Concentricity can only be applied on an RFS basis.

Location (Symmetry) Datum Features at RFS 6.35 +/- 0.05 0.5 A

A

15.95 15.90

As Shown on Drawing Means This:

Center Plane of Datum Feature A

0.5 Wide Tolerance Zone

Derived Median Points Within the limits of size and regardless of feature size, all median points of opposed elements must lie between two parallel planes equally disposed about datum plane A, 0.5 apart. Symmetry can only be applied on an RFS basis.

True Position Quiz Answer questions #1-11 True or False

1. Positional tolerances are applied to individual or patterns of features of size.

2. Cylindrical tolerance zones more closely represent the functional requirements of a pattern of clearance holes.

3. True position tolerance values are used to calculate the minimum size of a feature required for assembly.

4. True position tolerances can control a feature’s size. 5. Positional tolerances are applied on an MMC, LMC, or RFS basis.

6. Composite true position tolerances should be avoided because it is overly restrictive and difficult to check.

7. Composite true position tolerances can only be applied to patterns of related features.

8. The tolerance value shown in the upper segment of a composite true position feature control frame applies to the location of a pattern of features to the specified datums.

9. The tolerance value shown in the lower segment of a composite true position feature control frame applies to the location of a pattern of features to the specified datums.

10. Positional tolerances can be used to control circularity 11.

True position tolerances can be used to control center distance relationships between features of size.

True Position Quiz Questions #1-9 Fill in blanks (choose from below)

1. Positional tolerance zones can be ___________, ___________, or spherical

2. ________________

are used to establish the true (theoretically exact) position of a feature from specified datums.

3. Positional tolerancing is a _____________

control.

4. Positional tolerance can apply to the ____ or ________________ a feature.

5. _____ and ________ fastener equations are used to determine appropriate clearance hole sizes for mating details

6. _________ tolerance zones are recommended to prevent fastener interference in mating details.

7. The tolerance shown in the upper segment of a composite true position feature control frame is called the ________________ tolerance zone.

8. The tolerance shown in the lower segment of a composite true position feature control frame is called the ________________ tolerance zone.

9. Functional gaging principles can be applied when __________ ________ condition is specified surface boundary floating feature-relating pattern-locating rectangular cylindrical 3-dimensional basic dimensions projected location maximum material fixed axis

of

Notes

Notes

Fixed and Floating Fastener Exercises

Floating Fasteners In applications where two or more mating details are assembled, and all parts have clearance holes for the fasteners, the floating fastener formula shown below can be used to calculate the appropriate hole sizes or positional tolerance requirements to ensure assembly. The formula will provide a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance

2x M10 X 1.5 (Reference)

H=F+T or T=H-F

A B

2x

General Equation Applies to Each Part Individually

H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter

10.50 +/- 0.25 ?.? M

Calculate Required Positional Tolerance

T=H-F H = Minimum Hole Size = F = Max. Fastener Size =

T = 10.25 -10 T = ______

A 2x

Calculate Nominal Size

??.?? +/- 0.25 0.5 M

remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.

H = F +T F = Max. Fastener Size = T = Positional Tolerance =

B

10.25 10

H = 10 + 0.50 H = ______

10 0.50

Floating Fasteners In applications where two or more mating details are assembled, and all parts have clearance holes for the fasteners, the floating fastener formula shown below can be used to calculate the appropriate hole sizes or positional tolerance requirements to ensure assembly. The formula will provide a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance

2x M10 X 1.5 (Reference)

H=F+T or T=H-F

A B

2x

General Equation Applies to Each Part Individually

H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter

10.50 +/- 0.25 0.25 M

Calculate Required Positional Tolerance

T=H-F H = Minimum Hole Size = F = Max. Fastener Size =

T = 10.25 -10 T = 0.25

A 2x

Calculate Nominal Size

10.75 +/- 0.25 0.5 M

remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.

H = F +T F = Max. Fastener Size = T = Positional Tolerance =

B

10.25 10

H= H=

10 0.5

10 + .5 10.5 Minimum

REMEMBER!!! All Calculations Apply at MMC

Fixed Fasteners In fixed fastener applications where two mating details have equal positional tolerances, the fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size and/or positional tolerance required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note that in this example the positional tolerances indicated are the same for both parts.)

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED 2x M10 X 1.5 (Reference)

General Equation Used When Positional Tolerances Are Equal 10

A

H=F+2T or T=(H-F)/2

B

H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter

Calculate Required Clearance Hole Size.

2x

+/- 0.25

??.?? 0.8 M

A

H = F + 2T Nominal Size (MMC For Calculations)

2X M10 X 1.5 0.8 M P 10

remember: the size tolerance must be added to the calculated MMC size to obtain the correct nominal value.

F = Max. Fastener Size = T = Positional Tolerance =

H = 10.00 + 2(0.8) H = _____ B

10.00 0.80

Fixed Fasteners In fixed fastener applications where two mating details have equal positional tolerances, the fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size and/or positional tolerance required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note that in this example the positional tolerances indicated are the same for both parts.)

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED 2x M10 X 1.5 (Reference)

General Equation Used When Positional Tolerances Are Equal 10

A

H=F+2T or T=(H-F)/2

B

H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter

Calculate Required Clearance Hole Size.

2x

11.85 0.8

+/- 0.25

M

A

H = F + 2T Nominal Size (MMC For Calculations)

2X M10 X 1.5 0.8 M P 10

remember: the size tolerance must be added to the calculated MMC size to obtain the correct nominal value.

F = Max. Fastener Size = T = Positional Tolerance =

10.00 0.80

H = 10.00 + 2(0.8) H = 11.60 Minimum B

REMEMBER!!! All Calculations Apply at MMC

Fixed Fasteners In fixed fastener applications where two mating details have equal positional tolerances, the fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size and/or positional tolerance required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note that in this example the positional tolerances indicated are the same for both parts.)

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED 2x M10 X 1.5 (Reference)

General Equation Used When Positional Tolerances Are Equal 10

A

H=F+2T or T=(H-F)/2

B

H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter

Calculate Required Clearance Hole Size.

2x

11.85 0.8

+/- 0.25

M

A

H = F + 2T Nominal Size (MMC For Calculations)

2X M10 X 1.5 0.8 M P 10

remember: the size tolerance must be added to the calculated MMC size to obtain the correct nominal value.

F = Max. Fastener Size = T = Positional Tolerance =

H = 10 + 2(0.8) H = 11.6 Minimum B

REMEMBER!!! All Calculations Apply at MMC

10 0.8

Fixed Fasteners In applications where two mating details are assembled, and one part has restrained fasteners, the fixed fastener formula shown below can be used to calculate appropriate hole sizes and/or positional tolerances required to ensure assembly. The formula will provide a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note: in this example the resultant positional tolerance is applied to both parts equally.)

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED 2x M10 X 1.5 (Reference)

General Equation Used When Positional Tolerances Are Equal 10

A

H=F+2T or T=(H-F)/2

B

H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter

2x

11.25 +/- 0.25 0.5 M

A

T = (H - F)/2 2X M10 X 1.5 0.5 M P 10

Nominal Size (MMC For Calculations)

Calculate Required Positional Tolerance . (Both Parts)

H = Minimum Hole Size = F = Max. Fastener Size =

T = (11 - 10)/2 T = 0.50

B REMEMBER!!! All Calculations Apply at MMC

11 10

Fixed Fasteners In fixed fastener applications where two mating details have unequal positional tolerances, the fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size and/or positional tolerances required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note that in this example the positional tolerances indicated are not equal.)

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED 2x M10 X 1.5

General Equation Used When Positional Tolerances Are Not Equal

(Reference)

10

H=F+(T1 + T2)

A

H = Min. diameter of clearance hole F = Maximum diameter of fastener T1= Positional tolerance (Part A) T2= Positional tolerance (Part B)

B

Calculate Required Clearance Hole Size.

2x

+/- 0.25

??.?? 0.5 M

A 2X M10 X 1.5 1 M P 10

Nominal Size (MMC For Calculations)

remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.

H=F+(T1 + T2) F = Max. Fastener Size = T1 = Positional Tol. (A) = T2 = Positional Tol. (B) =

H = 10+ (0.5 + 1) H = ____ B

10 0.50 1

Fixed Fasteners In fixed fastener applications where two mating details have unequal positional tolerances, the fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size and/or positional tolerances required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note that in this example the positional tolerances indicated are not equal.)

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED 2x M10 X 1.5

General Equation Used When Positional Tolerances Are Not Equal

(Reference)

H= F+(T1 + T2)

A

10

H = Min. diameter of clearance hole F = Maximum diameter of fastener T1= Positional tolerance (Part A) T2= Positional tolerance (Part B)

B

Calculate Required Clearance Hole Size.

2x

+/- 0.25

11.75 0.5 M

A 2X M10 X 1.5 1 M P 10

Nominal Size (MMC For Calculations)

remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.

H=F+(T1 + T2) F = Max. Fastener Size = T1 = Positional Tol. (A) = T2 = Positional Tol. (B) =

H = 10 + (0.5 + 1) H = 11.5 Minimum B REMEMBER!!! All Calculations Apply at MMC

10 0.5 1

Fixed Fasteners In applications where a projected tolerance zone is not indicated, it is necessary to select a positional tolerance and minimum clearance hole size combination that will allow for any out-of-squareness of the feature containing the fastener. The modified fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at the extreme positional tolerance.

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS NOT USED H

F

P

A

D

B

Calculate Nominal Size

2x

H= Min. diameter of clearance hole F= Maximum diameter of pin T1= Positional tolerance (Part A) T2= Positional tolerance (Part B) D= Min. depth of pin (Part A) P= Maximum projection of pin

??.?? +/-0.25 0.5 M

A 2x

remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.

H= F + T1 + T2 (1+(2P/D))

10.05 +/-0.05 0.5 M

F = Max. pin size T1 = Positional Tol. (A) T2 = Positional Tol. (B) = Min. pin depth = Max. pin projection

=

10 = 0.5 = 0.5 D = 20. P = 15

B

H = 10.00 + 0.5 + 0.5(1 + 2(15/20)) H= __________

Fixed Fasteners In applications where a projected tolerance zone is not indicated, it is necessary to select a positional tolerance and minimum clearance hole size combination that will allow for any out-of-squareness of the feature containing the fastener. The modified fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at the extreme positional tolerance.

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS NOT USED H

F

P

A

D

B

Calculate Nominal Size

2x

H= Min. diameter of clearance hole F= Maximum diameter of pin T1= Positional tolerance (Part A) T2= Positional tolerance (Part B) D= Min. depth of pin (Part A) P= Maximum projection of pin

12 +/-0.25 0.5 M

A 2x

H= F + T1 + T2 (1+(2P/D))

remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.

H= F + T1 + T2 (1+(2P/D))

10.05 +/-0.05 0.5 M

F = Max. pin size = 10 T1 = Positional tol. (A) = 0.5 T2 = Positional tol. (B) = 0.5 D = Min. pin depth = 20 P = Max. pin projection = 15

B

H = 10 + 0.5 + 0.5(1 + 2(15/20)) H= 11.75 Minimum

REMEMBER!!! All Calculations Apply at MMC

Answers to Quizzes and Exercises

Rules and Definitions Quiz Questions #1-12 True or False

1.

Tight tolerances ensure high quality and performance.

FALSE

2.

The use of GD&T improves productivity.

TRUE

3.

Size tolerances control both orientation and position.

FALSE

4.

Unless otherwise specified size tolerances control form.

TRUE

5.

A material modifier symbol is not required for RFS.

TRUE

6.

A material modifier symbol is not required for MMC.

FALSE

7.

Title block default tolerances apply to basic dimensions.

FALSE

8.

A surface on a part is considered a feature.

TRUE

9.

Bilateral tolerances allow variation in two directions.

TRUE

10.

A free state modifier can only be applied to a tolerance.

FALSE

11.

A free state datum modifier applies to “assists” & “rests”.

TRUE

12.

Virtual condition applies regardless of feature size.

FALSE

Material Condition Quiz Fill in blanks

Internal Features

MMC

LMC

10.75

11

23.45 +0.05/-0.25

23.2

23.5

123. 5 +/-0.1

123.4

123.6

.890

.895

10.75 +0.25/-0

.895 .890

External Features

MMC

10.75 +0/-0.25

10.75

10.5

23.5

23.2

23.45 +0.05/-0.25 123. 5 +/-0.1 .890 .885

LMC

123.6

123.4

.890

.885

Calculate appropriate values

Datum Quiz Questions #1-12 True or False

1.

Datum target areas are theoretically exact.

FALSE

2.

Datum features are imaginary.

FALSE

3.

Primary datums have only three points of contact.

FALSE

4.

The 6 Degrees of Freedom are U/D, F/A, & C/C.

FALSE

5.

Datum simulators are part of the gage or tool.

TRUE

6.

Datum simulators are used to represent datums.

TRUE

7.

Datums are actual part features.

FALSE

8.

All datum features must be dimensionally stable.

TRUE

9.

Datum planes constrain degrees of freedom.

TRUE

10.

Tertiary datums are not always required.

TRUE

11.

All tooling locators (CD’s) are used as datums.

FALSE

12.

Datums should represent functional features.

TRUE

Datum Quiz Questions #1-10 Fill in blanks (choose from below)

1. The three planes that make up a basic datum reference frame are called primary, secondary, and tertiary.

2. An unrestrained part will exhibit 3-linear and 3-rotational degrees of freedom.

3. A planar primary datum plane will restrain 1-linear and 2-rotational degrees of freedom.

4. The primary and secondary datum planes together will restrain five degrees of freedom.

5. The primary, secondary and tertiary datum planes together will restrain all six degrees of freedom.

6. The purpose of a datum reference frame is to restrain movement of a part in a gage or tool.

7. A datum must be functional, repeatable, and coordinated. 8. A datum feature is an actual feature on a part. 9. A datum is a theoretically exact point, axis or plane. 10. A datum simulator is a precise surface used to establish a simulated datum.

restrain movement five coordinated repeatable tertiary two 3-rotational primary 2-rotational three functional one datum simulator 1-linear datum feature datum secondary 3-linear six

Form Control Quiz Questions #1-5 Fill in blanks (choose from below)

1. The four form controls are straightness, flatness, circularity, and cylindricity.

2. Rule #1 states that unless otherwise specified a feature of size must have perfect form at MMC.

3. Straightness and circularity are individual line or circular element (2-D) controls.

4. Flatness and cylindricity are surface (3-D) controls. 5. Circularity can be applied to both straight and tapered cylindrical parts.

straightness straight perfect form

cylindricity angularity flatness tapered profile circularity true position

Answer questions #6-10 True or False

6. Form controls require a datum reference.

FALSE

7. Form controls do not directly control a feature’s size.

TRUE

8. A feature’s form tolerance must be less than it’s size

TRUE

tolerance.

9. Flatness controls the orientation of a feature. 10. Size limits implicitly control a feature’s form.

FALSE TRUE

Orientation Control Quiz Questions #1-5 Fill in blanks (choose from below)

1. The three orientation controls are angularity, parallelism, and perpendicularity.

2. A datum reference is always required when applying any of the orientation controls.

3. Perpendicularity is the appropriate geometric tolerance when controlling the orientation of a feature at right angles to a datum reference.

4. Mathematically all three orientation tolerances are identical. 5. Orientation tolerances do not control the location of a feature. perpendicularity datum feature angularity

datum target location identical

datum reference parallelism profile

Answer questions #6-10 True or False

6. Orientation tolerances indirectly control a feature’s form.

TRUE

7. Orientation tolerance zones can be cylindrical.

TRUE

8. To apply a perpendicularity tolerance the desired angle

FALSE

must be indicated as a basic dimension.

9. Parallelism tolerances do not apply to features of size.

FALSE

10. To apply an angularity tolerance the desired angle must

TRUE

be indicated as a basic dimension.

Runout Control Quiz Answer questions #1-12 True or False

1. Total runout is a 2-dimensional

control.

FALSE

2. Runout tolerances are used on rotating parts.

TRUE

3. Circular runout tolerances apply to single elements .

TRUE

4. Total runout tolerances should be applied at MMC.

FALSE

5. Runout tolerances can be applied to surfaces at right

TRUE

angles to the datum reference.

6. Circular runout tolerances are used to control an entire

FALSE

feature surface.

7. Runout tolerances always require a datum reference.

TRUE

8. Circular runout and total runout both control axis to

TRUE

surface relationships.

9. Circular runout can be applied to control taper of a part. 10. Total runout tolerances are an appropriate way to limit

FALSE TRUE

“wobble” of a rotating surface.

11.

Runout tolerances are used to control a feature’s size.

12. Total runout can control circularity, straightness, taper, coaxiality, angularity and any other surface variation.

FALSE TRUE

Profile Control Quiz Questions #1-9 Fill in blanks (choose from below)

1. The two types of profile tolerances are profile of a line, and profile of a surface. 2. Profile tolerances can be used to control the location, form, orientation, and sometimes size of a feature.

3. Profile tolerances can be applied bilateral or unilateral. 4. Profile of a line tolerances are 2-dimensional controls. 5. Profile of a surface tolerances are 3-dimensional controls. 6. Composite Profile can be used when different tolerances are required for location and form and/or orientation.

7. When using profile tolerances to control the location and/or orientation of a feature, a datum reference must be included in the feature control frame.

8. When using profile tolerances to control form only, a datum reference is not required in the feature control frame.

9. In composite profile applications, the tolerance shown in the upper segment of the feature control frame applies only to the location of the feature.

composite profile bilateral virtual condition profile of a surface primary datum orientation datum reference unilateral profile of a line location true geometric counterpart form

Profile Control Quiz Answer questions #1-13 True or False

1. Profile tolerances always require a datum reference.

FALSE

2. Profile of a surface tolerance is a 2-dimensional control. FALSE 3. Profile of a surface tolerance should be used to control

TRUE

4. Profile of a line tolerances should be applied at MMC.

FALSE

5. Profile tolerances can be applied to features of size.

TRUE

trim edges on sheet metal parts.

6. Profile tolerances can be combined with other geometric TRUE controls such as flatness to control a feature.

7. Profile of a line tolerances apply to an entire surface.

FALSE

8. Profile of a line controls apply to individual line elements. TRUE 9. Profile tolerances only control the location of a surface.

FALSE

10. Composite profile controls should be avoided because

FALSE

11. Profile tolerances can be applied either bilateral or

TRUE

12. Profile tolerances can be applied in both freestate and

TRUE

13. Tolerances shown in the lower segment of a composite

FALSE

they are more restrictive and very difficult to check. unilateral to a feature.

restrained datum conditions.

profile feature control frame control the location of a feature to the specified datums.

True Position Quiz Answer questions #1-11 True or False

1. Positional tolerances are applied to individual or patterns TRUE of features of size.

2. Cylindrical tolerance zones more closely represent the

TRUE

functional requirements of a pattern of clearance holes.

3. True position tolerance values are used to calculate the

TRUE

4. True position tolerances can control a feature’s size.

FALSE

5. Positional tolerances are applied on an MMC, LMC, or

TRUE

6. Composite true position tolerances should be avoided

FALSE

7. Composite true position tolerances can only be applied

TRUE

8. The tolerance value shown in the upper segment of a

TRUE

9. The tolerance value shown in the lower segment of a

FALSE

10. Positional tolerances can be used to control circularity

FALSE TRUE

minimum size of a feature required for assembly.

RFS basis.

because it is overly restrictive and difficult to check. to patterns of related features.

composite true position feature control frame applies to the location of a pattern of features to the specified datums. composite true position feature control frame applies to the location of a pattern of features to the specified datums.

11. True position tolerances can be used to control center distance relationships between features of size.

True Position Quiz Questions #1-9 Fill in blanks (choose from below)

1. Positional tolerance zones can be rectangular, cylindrical, or spherical

2. Basic dimensions are used to establish the true (theoretically exact) position of a feature from specified datums.

3. Positional tolerancing is a 3-dimensional control.

4. Positional tolerance can apply to the axis or surface boundary of a feature.

5. Fixed and floating fastener equations are used to determine appropriate clearance hole sizes for mating details

6. Projected tolerance zones are recommended to prevent fastener interference in mating details.

7. The tolerance shown in the upper segment of a composite true position feature control frame is called the pattern-locating tolerance zone.

8. The tolerance shown in the lower segment of a composite true position feature control frame is called the feature-relating tolerance zone.

9. Functional gaging principles can be applied when maximum material condition is specified

surface boundary floating feature-relating pattern-locating rectangular cylindrical 3-dimensional basic dimensions projected location maximum material fixed axis

E N D

Notes

Notes

Notes

Extreme Variations of Form Allowed By Size Tolerance

25 (MMC)

25.1 25

25 24.9

25.1 (LMC)

25 (MMC)

24.9 (LMC)

25.1 (LMC)

25 (MMC)

24.9 (LMC)

MMC Perfect Form Boundary

25.1 (LMC)

24.9 (LMC)

25 (MMC)

Virtual and Resultant Condition Boundaries Internal and External Features (MMC Concept)

Virtual Condition Boundary Internal Feature (MMC Concept) 14 +/- 0.5 1M A B C

A

C XX.X

B

XX.X

As Shown on Drawing

(

Virtual Condition Inner Boundary Maximum Inscribed Diameter

1 Positional Tolerance Zone at MMC

)

True (Basic) Position of Hole Other Possible Extreme Locations Boundary of MMC Hole Shown at Extreme Limit

True (Basic) Position of Hole

Calculating Virtual Condition 13.5 1

MMC Size of Feature Applicable Geometric Tolerance

12.5

Virtual Condition Boundary

Axis Location of MMC Hole Shown at Extreme Limit

Resultant Condition Boundary Internal Feature (MMC Concept) 14 +/- 0.5 1M A B C

A

C XX.X

B

XX.X

As Shown on Drawing

(

Resultant Condition Outer Boundary Minimum Circumscribed Diameter

2 Positional Tolerance Zone at LMC

)

True (Basic) Position of Hole Other Possible Extreme Locations Boundary of LMC Hole Shown at Extreme Limit

True (Basic) Position of Hole

Calculating Resultant Condition (Internal Feature) 14.5 2

LMC Size of Feature Geometric Tolerance (at LMC)

16.5

Resultant Condition Boundary

Axis Location of LMC Hole Shown at Extreme Limit

Virtual Condition Boundary External Feature (MMC Concept) 14 +/- 0.5 1M A B C

A

C XX.XX

B

XX.X

As Shown on Drawing

(

Virtual Condition Outer Boundary Minimum Circumscribed Diameter

1 Positional Tolerance Zone at MMC

)

True (Basic) Position of Feature Other Possible Extreme Locations Boundary of MMC Feature Shown at Extreme Limit

True (Basic) Position of Feature

Calculating Virtual Condition 14.5 1

MMC Size of Feature Applicable Geometric Tolerance

15.5

Virtual Condition Boundary

Axis Location of MMC Feature Shown at Extreme Limit

Resultant Condition Boundary External Feature (MMC Concept) 14 +/- 0.5 1M A B C

A

C XX.X

B

XX.X

As Shown on Drawing

(

Resultant Condition Inner Boundary Maximum Inscribed Diameter

2 Positional Tolerance Zone at LMC

)

True (Basic) Position of Feature Other Possible Extreme Locations Boundary of LMC feature Shown at Extreme Limit

True (Basic) Position of Feature

Axis Location of LMC Feature Shown at Extreme Limit

Calculating Resultant Condition (External Feature) 13.5 2

LMC Size of Feature Geometric Tolerance (at LMC)

11.5

Resultant Condition Boundary

• 3X 5.0  5mm is 3 times repeated. A space is used after X Maximum Material Condition (MMC): The condition where the feature contains the maximum material within the stated limits of size – for example, the largest pin or the smallest hole.

Least Material Condition (LMC): The condition where the feature contains the least material with in the stated limits of size - for example, the smallest pin or largest hole.

GEOMETRIC CHARACTERISTIC SYMBOLS TYPE OF TOLERANCE

CHARACTERISTIC

STRAIGHNESS FOR INDIVIDUAL FEATURES

FORM

FLATNESS CIRCULARITY (ROUNDNESS) CYLINDRICITY

FOR INDIVIDUAL OR RELATED FEATURES

FROFILE

PROFILE OF A SURFACE PROFILE OF A LINE ANGULARITY

ORIENTATION

PERPENDICULARITY

PARALLELISM FOR RELATED FEATURES

POSITION CONCENTRICITY

LOCATION SYMMETRY

RUNOUT

CIRCULAR RUNOUT TOTAL RUNOUT

SYMBOL