Based on the ASME Y14.5M
Based on the ASME Y14.5M
-
-1994 Dimensioning and
1994 Dimensioning and
Tolerancing Standard
Tolerancing Standard
DIMENSIONAL
ENGINEERING
Tolerances
of Form
Straightness Flatness Circularity Cylindricity (ASME Y14.5M-1994, 6.4.1) (ASME Y14.5M-1994, 6.4.3) (ASME Y14.5M-1994, 6.4.2) (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)
25.1
(LMC)
MMC Perfect
Form Boundary
Extreme Variations of Form
Allowed By Size Tolerance
25 24.9
25
(MMC)
24.9
(LMC)
24.9
(LMC)
MMC Perfect
Form Boundary
25
(MMC)
24.9
(LMC)
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)
Straightness
(Flat Surfaces)
24.75 min
25.25 max
0.5 Tolerance Zone
0.1 Tolerance Zone
The straightness tolerance is applied in the view where the
elements to be controlled are represented by a straight line
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.
Straightness
(Surface Elements)
MMC 0.1 Tolerance Zone 0.1 MMC 0.1 Tolerance Zone MMC 0.1 Tolerance ZoneIn 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
Straightness (RFS)
Straightness (RFS)
Straightness (RFS)
Straightness (RFS)
0.1
Outer Boundary (Max) MMC
0.1 Diameter Tolerance Zone
Outer Boundary = Actual Feature Size + Straightness Tolerance
Outer Boundary = Actual Feature Size + Straightness Tolerance
Outer Boundary = Actual Feature Size + Straightness Tolerance
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
Straightness (MMC)
15 14.85 15.1 Virtual Condition 15 (MMC) 0.1 Diameter Tolerance Zone 15.1 Virtual Condition 14.85 (LMC) 0.25 Diameter Tolerance ZoneVirtual 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
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.
25 +/-0.25
24.75 min 25.25 max
0.1
0.1 Tolerance Zone
0.1 Tolerance Zone
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.
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
90
90 0.1
0.1 Wide Tolerance Zone
Circularity
(Roundness)
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.
Cylindricity
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.
0.1 Tolerance Zone
MMC 0.1
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.
____________
and___________
are individual line or circular element (2-D) controls.Form Control Quiz
The four form controls are
____________
,________
,___________
, and____________
.Rule #1 states that unless otherwise specified a feature of size must have
____________
at MMC.________
and____________
are surface (3-D) controls.Circularity can be applied to both
________
and_______
cylindrical parts.1.
2.
3.
4.
5.
Form controls require a datum reference.
Form controls do not directly control a feature’s size. A feature’s form tolerance must be less than it’s size tolerance.
Flatness controls the orientation of a feature. Size limits implicitly control a feature’s form.
6.
7.
8.
9.
10.
Questions #1-5 Fill in blanks (choose from below)
straightness
flatness
circularity
cylindricity
perfect form
straight
tapered
profile
true position
angularity
Tolerances of
Orientation
Angularity Perpendicularity Parallelism (ASME Y14.5M-1994 ,6.6.2) (ASME Y14.5M-1994 ,6.6.4) (ASME Y14.5M-1994 ,6.6.3)Angularity
(Feature Surface to Datum Surface)
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.
A
20 +/-0.5 30 oA
19.5 min 0.3 Wide Tolerance Zone 30 oA
20.5 max 0.3 Wide Tolerance Zone 30 oThe 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 feature axis at a specified
angle (other than 90 degrees) to the datum reference plane,
within the specified tolerance zone.
A
0.3 A
A
60 o
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.
0.3 Circular Tolerance Zone
0.3 Circular Tolerance Zone
Angularity
(Feature Axis to Datum Surface)
NOTE: Tolerance applies
to feature at RFS
0.3 Circular Tolerance Zone
NOTE: Tolerance
applies to feature
at RFS
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.
0.3 Circular Tolerance Zone
A
Datum Axis A
Angularity
(Feature Axis to Datum Axis)
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.
NOTE: Feature axis must lie
within tolerance zone cylinder
0.3 A
o
0.3 A
A
0.3 Wide
Tolerance Zone
A
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 Surface to Datum Surface)
0.3 Wide
Tolerance Zone
The tolerance zone in this example is
defined by two parallel planes oriented
perpendicular to the datum reference
plane.
C
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 Surface)
0.3 C 0.3 Circular Tolerance Zone 0.3 Diameter Tolerance Zone 0.3 Circular Tolerance Zone
NOTE: Tolerance applies
to feature at RFS
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
(Feature Axis to Datum Axis)
NOTE: Tolerance applies
to feature at RFS
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.
0.3 Wide Tolerance ZoneA
Datum Axis A
0.3 A0.3 A
A
25 +/-0.5
25.5 max
0.3 Wide Tolerance Zone
A
24.5 min
0.3 Wide Tolerance Zone
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 Surface to Datum Surface)
The tolerance zone in this example
is defined by two parallel planes
oriented parallel to the datum
reference plane.
A
0.3 Wide
Tolerance Zone
Parallelism
(Feature Axis to Datum Surface)
0.3 A
A
NOTE: The specified tolerance
does not apply to the orientation
of the feature axis in this direction
Parallelism is the condition of the feature axis equidistant
along its length from the datum reference plane, within the
specified tolerance zone.
The tolerance zone in this example
is defined by two parallel planes
oriented parallel to the datum
reference plane.
NOTE: Tolerance applies
to feature at RFS
A
B
Parallelism
(Feature Axis to Datum Surfaces)
A
B
0.3 Circular Tolerance Zone 0.3 Circular Tolerance Zone 0.3 Circular Tolerance ZoneParallelism is the condition of the feature axis equidistant
along its length from the two datum reference planes, within
the specified tolerance zone.
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.
NOTE: Tolerance applies
to feature at RFS
Parallelism
(Feature Axis to Datum Axis)
Parallelism is the condition of the feature axis equidistant along
its length from the datum reference axis, within the specified
tolerance zone.
A
0.1 A 0.1 Circular Tolerance Zone 0.1 Circular Tolerance ZoneDatum Axis 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 axis.
NOTE: Tolerance applies
to feature at RFS
Orientation Control Quiz
The three orientation controls are
__________
,___________
, and________________
.1.
2.
3.
4.
5.
A
_______________
is always required when applying any of the orientation controls.________________
is the appropriate geometric tolerance when controlling the orientation of a feature at right angles to a datumreference.
Orientation tolerances indirectly control a feature’s form.
Mathematically all three orientation tolerances are
_________
. Orientation tolerances do not control the________
of a feature.6.
Orientation tolerance zones can be cylindrical.
Parallelism tolerances do not apply to features of size. To apply an angularity tolerance the desired angle must be indicated as a basic dimension.
7.
8.
9.
10.
To apply a perpendicularity tolerance the desired angle must be indicated as a basic dimension.
Questions #1-5 Fill in blanks (choose from below)
angularity
perpendicularity
parallelism
datum reference
identical
location
profile
datum feature
datum target
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)Datum feature
Datum axis (established
from datum feature
Angled surfaces
constructed around
a datum axis
External surfaces
constructed around
a datum axis
Internal surfaces
constructed around a
datum axis
Surfaces constructed
perpendicular to a
datum axis
Features Applicable
to Runout Tolerancing
0
+
-Full Indicator Movement Maximum Minimum Total Tolerance Maximum Reading Minimum Reading Full Part Rotation Measuring position #1 (circular element #1)Circular Runout
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 2-dimensional wobble (orientation) and waviness (form), but not 3-2-dimensional characteristics such as surface profile (overall form) or surface wobble (overall orientation).
Measuring position #2 (circular element #2)
Circular runout can only be applied on an RFS basis and cannot be modified to MMC or LMC.
o 360 Part Rotation 50 o +/- 2o
As Shown
on Drawing
Means This:
Datum axis A Single circular elementCircular Runout
(Angled Surface to Datum Axis)
0.75 A A 50 +/-0.25 0 +
-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
Full Indicator Movement
(
)
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.
When measuring circular runout, the indicator must be reset when repositioned along the feature surface.
As Shown
on Drawing
50 +/-0.25
0.75 A
Circular Runout
(Surface Perpendicular to Datum Axis)
o 360 Part Rotation 0 + -Datum axis A Single circular element
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 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.
Means This:
Allowable indicator reading = 0.75 max.
When measuring circular runout, the indicator must be reset when repositioned along the feature surface.
0
+ -Allowable indicator
reading = 0.75 max.
Single circular element o 360 Part Rotation
Means This:
As Shown
on Drawing
50 +/-0.25 0.75 A Datum axis AWhen measuring circular runout, the indicator must be reset when repositioned along the feature surface.
Circular Runout
(Surface Coaxial to Datum Axis)
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.
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
0
+ -Allowable indicator
reading = 0.75 max.
Single circular element
o 360 Part Rotation
Means This:
As Shown
on Drawing
0.75 A-BDatum axis A-B
When measuring circular runout, the indicator must be reset when repositioned along the feature surface.
Circular Runout
(Surface Coaxial to Datum Axis)
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.
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
Machine center Machine center B A
As Shown
on Drawing
50 +/-0.25
Circular Runout
(Surface Related to Datum Surface and Axis)
o 360 Part Rotation 0 + -Datum axis B 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 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:
A
Allowable indicator reading = 0.75 max.
When measuring circular runout, the indicator must be reset when repositioned along the feature surface. Collet or Chuck Stop collar 0.75 A B Datum plane A B
0
+
Full Indicator Movement Total Tolerance Maximum Reading Minimum Reading Full Part Rotation -0+
-Total Runout
Maximum MinimumWhen 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).
Indicator Path
Total runout can only be applied on an RFS basis and cannot be modified to MMC or LMC.
Full Part Rotation 50 o +/- 2o
As Shown
on Drawing
A 50 +/-0.25 0.75 AMeans This:
Datum axis A 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.
0
+
-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
(Angled Surface to Datum Axis)
Collet or Chuck
When measuring total runout, the indicator must not be reset when repositioned along the feature surface.
(applies to the entire feature surface) Allowable indicator reading = 0.75 max.
0
+
-Total Runout
(Surface Perpendicular to Datum Axis)
As Shown
on Drawing
A 50 +/-0.25 0.75 A 35 10 0 + -Datum axis A Full Part Rotation 35 10Means This:
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.
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.
When measuring total runout, the indicator must not be reset when repositioned along the feature surface.
(applies to portion of feature surface indicated) Allowable indicator reading = 0.75 max.
Runout Control Quiz
Answer questions #1-12 True or False
Total runout is a 2-dimensional control.
1.
Runout tolerances are used on rotating parts.
Total runout tolerances should be applied at MMC. Runout tolerances can be applied to surfaces at right angles to the datum reference.
2.
3.
4.
5.
Circular runout tolerances apply to single elements .
6.
Circular runout tolerances are used to control an entire feature surface.Runout tolerances always require a datum reference.
7.
Circular runout and total runout both control axis to surface relationships.
8.
Circular runout can be applied to control taper of a part.
9.
Total runout tolerances are an appropriate way to limit “wobble” of a rotating surface.
10.
Runout tolerances are used to control a feature’s size.
11.
Total runout can control circularity, straightness, taper, coaxiality, angularity and any other surface variation.
Tolerances
of Profile
Profile of a Line
Profile of a Surface
(ASME Y14.5M-1994, 6.5.2b)
18 Max
Profile of a Line
2 Wide Size Tolerance Zone 1 A B C A 17 +/- 1 1 Wide Profile Tolerance Zone C A1 20 X 20 A2 20 X 20 A3 20 X 20 BThe 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 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
2 Wide Tolerance Zone
Size, Form and Orientation
A A1 20 X 20 A2 20 X 20 A3 20 X 20 C 2 A B C 23.5 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
A1 20 X 20 A2 20 X 20 A3 20 X 20 B C 50 B C 50 1 Wide Total Tolerance Zone(Bilateral Tolerance)
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.
1 A B C
Nominal Location 0.5 Inboard
0.5 Outboard
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
A1 20 X 20 A2 20 X 20 A3 20 X 20 B C 50 B C 50 0.5 Wide Total Tolerance Zone(Unilateral Tolerance)
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.
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.
0.5 A B C
Profile of a Surface
A1 20 X 20 A2 20 X 20 A3 20 X 20 B C 50 1.2 A B C B C 50 0.5 Inboard 0.7 Outboard 1.2 Wide Total Tolerance Zone(Unequal Bilateral Tolerance)
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.
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).
0.5
A 25 A 0.5 0.1 25.25 24.75 0.1 Wide Tolerance Zone
A
Composite Profile of Two Coplanar
Surfaces w/o Orientation Refinement
Profile of a Surface
Form Only Location & Orientation
0.1 Wide Tolerance Zone
0.1 Wide Tolerance Zone 25.25 24.75 A A A 25 A 0.5 A
0.1 Form & Orientation
Composite Profile of Two Coplanar
Surfaces With Orientation Refinement
Profile of a Surface
6.
Profile Control Quiz
Profile tolerances always require a datum reference.
Answer questions #1-13 True or False
1.
Profile of a surface tolerance is a 2-dimensional control.
Profile of a line tolerances should be applied at MMC. Profile tolerances can be applied to features of size.
2.
3.
4.
5.
Profile of a surface tolerance should be used to control trim edges on sheet metal parts.
Profile tolerances can be combined with other geometric controls such as flatness to control a feature.
Profile of a line tolerances apply to an entire surface.
7.
Profile of a line controls apply to individual line elements.
8.
Profile tolerances only control the location of a surface.
9.
Composite profile controls should be avoided because they are more restrictive and very difficult to check.
10.
Profile tolerances can be applied either bilateral or unilateral to a feature.
11.
Profile tolerances can be applied in both freestate and restrained datum conditions.
12.
Tolerances shown in the lower segment of a composite profile feature control frame control the location of a feature to the specified datums.
In composite profile applications, the tolerance shown in the upper segment of the feature control frame applies only to the
________
of the feature.Profile Control Quiz
The two types of profile tolerances are
_________________
, and____________________.
1.
2.
3.
4.
5.
Profile tolerances can be used to control the
________
,____
,___________
, and sometimes size of a feature.Profile tolerances can be applied
_________
or__________.
_________________
tolerances are 2-dimensional controls.____________________
tolerances are 3-dimensional controls.Questions #1-9 Fill in blanks (choose from below)
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 includedin the feature control frame.
8.
When using profile tolerances to control form only, a______
__________
is not required in the feature control frame.9.
profile of a line
datum reference
composite profile
bilateral
location
form
primary datum
true geometric counterpart
orientation
profile of a surface
unilateral
Tolerances
of Location
True Position Concentricity Symmetry (ASME Y14.5M-1994, 5.2) (ASME Y14.5M-1994, 5.12) (ASME Y14.5M-1994, 5.13)10.25 +/- 0.5 10.25 +/- 0.5 8.5 +/- 0.1 Rectangular Tolerance Zone 10.25 10.25 8.5 +/- 0.1 Circular Tolerance Zone B A C
Coordinate vs Geometric
Tolerancing Methods
Coordinate Dimensioning
Geometric Dimensioning
Rectangular Tolerance Zone Circular Tolerance Zone 1.4 +/- 0.5
+/- 0.5
57% Larger
Tolerance Zone
Circular Tolerance Zone
Rectangular Tolerance Zone
Increased Effective Tolerance
Formula to determine the actual radial
position of a feature using measured
coordinate values (RFS)
Z
positional tolerance /2
X
2
+
Y
2
Z =
X =
2
Y =
2
X
Y
Z
Feature axis actual
location (measured)
Positional
tolerance zone
cylinder
Feature axis true
position (designed)
Positional Tolerance Verification
Z = total radial deviation
“X” measured deviation
“Y” measured deviation
Actual feature
boundary
Formula to determine the actual radial
position of a feature using measured
coordinate values (MMC)
Z
X
2
+
Y
2
Z =
X =
2
Y =
2
X
Y
Z
Feature axis actual
location (measured)
Positional
tolerance zone
cylinder
Feature axis true
position (designed)
Positional Tolerance Verification
Z = total radial deviation
“X” measured deviation
“Y” measured deviation
Actual feature
boundary
+( actual -
MMC)
2
= positional tolerance
Bi-directional True Position
Rectangular Coordinate Method
35 10 10
A
C
B
1.5 A B C 0.5 A B C2X
2X
10 35 1.5 Wide Tolerance Zone 0.5 Wide Tolerance Zone True Position Relatedto Datum Reference Frame
10
B
C
Each axis must lie within the 1.5 X 0.5 rectangular tolerance zone
basically located to the datum reference frame
As Shown
on Drawing
Means This:
Bi-directional True Position
Multiple Single-Segment Method
35 10 10
A
C
B
10 35 1.5 Wide Tolerance Zone 0.5 Wide Tolerance Zone True Position Relatedto Datum Reference Frame
10
B
C
Each axis must lie within the 1.5 X 0.5 rectangular tolerance zone
basically located to the datum reference frame
As Shown
on Drawing
Means This:
2X 6 +/-0.25
1.5 A B C 0.5 A B35 10 10
A
C
B
As Shown
on Drawing
Means This:
1.5 A B C 0.5 A B C BOUNDARY BOUNDARY 10 35 10B
C
2X 13 +/-0.25 2X 6 +/-0.25 12.75MMC width of slot -1.50Position tolerance 11.25 Maximum boundaryBoth 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.
o
90
True position boundary related to datum reference frame
A
Bi-directional True Position
Noncylndrical Features (Boundary Concept)
M M
5.75 MMC length of slot
-0.50Position tolerance
Composite True Position
Without Pattern Orientation Control
35 10 10
A
C
B
10 35True Position Related to Datum Reference Frame
10
B
C
Each axis must lie within each tolerance zone simultaneously
As Shown
on Drawing
Means This:
2X 6 +/-0.25
1.5 A B C 0.5 A 0.5 Feature-Relating Tolerance Zone Cylinder1.5 Pattern-Locating Tolerance Zone Cylinder
pattern location relative to Datums A, B, and C pattern orientation relative to
Composite True Position
With Pattern Orientation Control
35 10 10
A
C
B
10 35True Position Related to Datum Reference Frame
10
B
C
Each axis must lie within each tolerance zone simultaneously
As Shown
on Drawing
Means This:
2X 6 +/-0.25
0.5 Feature-Relating Tolerance Zone Cylinder
1.5 Pattern-Locating Tolerance Zone Cylinder
pattern location relative to Datums A, B, and C
pattern orientation relative to Datums A and B
1.5 A B C 0.5 A B
Location (Concentricity)
Datum Features at RFS
A
15.95
15.90
As Shown on Drawing
Derived Median Points of Diametrically Opposed Elements
Axis of Datum Feature A
Means This:
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.
0.5 A
6.35 +/- 0.05
0.5 Coaxial Tolerance Zone
Location (Symmetry)
Datum Features at RFS
A
15.95
15.90
0.5 A
6.35 +/- 0.05
Derived Median Points Center Plane of Datum Feature A 0.5 Wide Tolerance ZoneMeans This:
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
Positional tolerances are applied to individual or patterns of features of size.
1.
Cylindrical tolerance zones more closely represent the functional requirements of a pattern of clearance holes.
True position tolerances can control a feature’s size. Positional tolerances are applied on an MMC, LMC, or RFS basis.
2.
3.
4.
5.
True position tolerance values are used to calculate the minimum size of a feature required for assembly.
6.
Composite true position tolerances should be avoided because it is overly restrictive and difficult to check. Composite true position tolerances can only be applied to patterns of related features.7.
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.
8.
Positional tolerances can be used to control circularity
9.
10.
11.
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.
True position tolerances can be used to control center distance relationships between features of size.
Positional tolerance zones can be
___________
,___________
, or spherical1.
2.
3.
4.
5.
________________
are used to establish the true (theoretically exact) position of a feature from specified datums.Positional tolerancing is a
_____________
control.Positional tolerance can apply to the
____
or________________
of a feature._____
and________
fastener equations are used to determine appropriate clearance hole sizes for mating details6.
7.
_________
tolerance zones are recommended to prevent fastener interference in mating details.8.
projected
3-dimensional
surface boundary
floating
location
fixed
basic dimensions
maximum material
cylindrical
pattern-locating
rectangular
feature-relating
True Position Quiz
Questions #1-9 Fill in blanks (choose from below)
The tolerance shown in the upper segment of a composite true
position feature control frame is called the
________________
tolerance zone.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 specifiedFixed and
Floating
Fastener
Exercises
2x M10 X 1.5 (Reference)
B
A
?.? 2x 10.50 +/- 0.25 M Calculate Required Positional Tolerance 0.5 2x ??.?? +/- 0.25 M Calculate Nominal SizeA
B
T = H - F
H = Minimum Hole Size = 10.25 F = Max. Fastener Size = 10
T = 10.25 -10
T = ______
Floating Fasteners
H = F +T
F = Max. Fastener Size = 10 T = Positional Tolerance = 0.50
H = 10 + 0.50
H = ______
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
H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter
H=F+T or T=H-F
General Equation Applies to Each Part Individually
remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.
2x M10 X 1.5 (Reference)
B
A
0.25 2x 10.50 +/- 0.25 M 0.5 2x 10.75 +/- 0.25 MA
B
Floating Fasteners
REMEMBER!!! All Calculations Apply at MMC
H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter
H=F+T or T=H-F
General Equation Applies to Each Part Individually
T = H - F
H = Minimum Hole Size = 10.25 F = Max. Fastener Size = 10
T = 10.25 -10
T = 0.25
Calculate Required Positional Tolerance
F = Max. Fastener Size = 10 T = Positional Tolerance = 0.5
H = 10 + .5
H = 10.5 Minimum
H = F +T
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
remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.
Calculate Nominal Size
F = Max. Fastener Size = 10.00 T = Positional Tolerance = 0.80 2x M10 X 1.5 (Reference)
B
A
0.8 2x ??.?? +/- 0.25 M Calculate Required Clearance Hole Size.2X M10 X 1.5
A
B
Fixed Fasteners
H = 10.00 + 2(0.8)
H = _____
H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter
H=F+2T or T=(H-F)/2
General Equation Used When Positional Tolerances Are Equal
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.)
0.8 M P10
APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED
Nominal Size (MMC For Calculations)
H = F + 2T
remember: the size tolerance must be added to the calculated MMC size to obtain the correct nominal value.
2x M10 X 1.5 (Reference)
B
A
2x 11.85 +/- 0.25 0.8 M Calculate Required Clearance Hole Size.A
B
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.)
Fixed Fasteners
H = F + 2T
F = Max. Fastener Size = 10.00 T = Positional Tolerance = 0.80
H = 10.00 + 2(0.8)
H = 11.60 Minimum
H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameterH=F+2T or T=(H-F)/2
General Equation Used When Positional Tolerances Are Equal
0.8 M P10
APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED
2X M10 X 1.5 (MMC For Calculations)Nominal Size
remember: the size tolerance must be added to the calculated MMC size to obtain the correct nominal value.
REMEMBER!!! All Calculations Apply at MMC
2x M10 X 1.5 (Reference)
B
A
2x 11.85 +/- 0.25 0.8 M Calculate Required Clearance Hole Size.A
B
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.)
Fixed Fasteners
H = F + 2T
F = Max. Fastener Size = 10 T = Positional Tolerance = 0.8
H = 10 + 2(0.8)
H = 11.6 Minimum
H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameterH=F+2T or T=(H-F)/2
General Equation Used When Positional Tolerances Are Equal
0.8 M P10
APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED
2X M10 X 1.5 (MMC For Calculations)Nominal Size
remember: the size tolerance must be added to the calculated MMC size to obtain the correct nominal value.
REMEMBER!!! All Calculations Apply at MMC
2x M10 X 1.5 (Reference)
B
A
0.5 2x 11.25 +/- 0.25M Calculate Required Positional Tolerance .
(Both Parts)
A
B
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.)
Fixed Fasteners
T = (H - F)/2
H = Minimum Hole Size = 11 F = Max. Fastener Size = 10
T = (11 - 10)/2
T = 0.50
H= Min. diameter of clearance hole F= Maximum diameter of fastener T= Positional tolerance diameter
H=F+2T or T=(H-F)/2
General Equation Used When Positional Tolerances Are Equal
2X M10 X 1.5 0.5 M P 10
APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED
Nominal Size (MMC For Calculations)
REMEMBER!!! All Calculations Apply at MMC
2x M10 X 1.5 (Reference)
B
A
0.5 2x ??.?? +/- 0.25 M Calculate Required Clearance Hole Size.A
B
Fixed Fasteners
H = Min. diameter of clearance hole F = Maximum diameter of fastener T1= Positional tolerance (Part A) T2=
Positional tolerance (Part B)
H=F+(T
1+ T
2)
General Equation Used When Positional Tolerances Are Not Equal
F = Max. Fastener Size = 10 T1= Positional Tol. (A) = 0.50
T2= Positional Tol. (B) = 1
H = 10+ (0.5 + 1)
H = ____
H=F+(T
1+ T
2)
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 (MMC For Calculations)Nominal Size
remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.
10
2x M10 X 1.5 (Reference)
B
A
0.5 2x 11.75 +/- 0.25 M Calculate Required Clearance Hole Size.A
B
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.)
Fixed Fasteners
F = Max. Fastener Size = 10 T1= Positional Tol. (A) = 0.5
T2= Positional Tol. (B) = 1
H = 10 + (0.5 + 1)
H = 11.5 Minimum
APPLIES WHEN A PROJECTED TOLERANCE ZONE IS USED
H = Min. diameter of clearance hole F = Maximum diameter of fastener T1= Positional tolerance (Part A) T2=
Positional tolerance (Part B)
H= F+(T
1+ T
2)
General Equation Used When Positional Tolerances Are Not Equal
H=F+(T
1+ T
2)
1 M P 10
2X M10 X 1.5 (MMC For Calculations)Nominal Size
remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.
REMEMBER!!! All Calculations Apply at MMC
D P
H F
A
B
APPLIES WHEN A PROJECTED TOLERANCE ZONE IS NOT USED
2x 10.05 +/-0.05
B
A
0.5 M 2x ??.?? +/-0.25 Calculate Nominal Size 0.5 MIn 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.
Fixed Fasteners
H =
10.00 + 0.5 + 0.5(1 + 2(15/20))H = __________
H= F + T
1+ T
2(1+(2P/D))
remember: the size tolerance must beadded to the calculated MMC hole size to obtain the correct nominal value.
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
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
D P
H F
A
B
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
APPLIES WHEN A PROJECTED TOLERANCE ZONE IS NOT USED
2x 10.05 +/-0.05
B
A
0.5 M 2x 12 +/-0.25 Calculate Nominal Size 0.5 MF = 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
H= F + T
1+ T
2(1+(2P/D))
H =
10 + 0.5 + 0.5(1 + 2(15/20))H = 11.75 Minimum
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.
Fixed Fasteners
H= F + T
1+ T
2(1+(2P/D))
REMEMBER!!! All Calculations Apply at MMC
remember: the size tolerance must be added to the calculated MMC hole size to obtain the correct nominal value.
Answers to Quizzes
and Exercises
Rules and Definitions Quiz
1. Tight tolerances ensure high quality and performance. 2. The use of GD&T improves productivity.
3. Size tolerances control both orientation and position. 4. Unless otherwise specified size tolerances control form. 5. A material modifier symbol is not required for RFS. 6. A material modifier symbol is not required for MMC. 7. Title block default tolerances apply to basic dimensions. 8. A surface on a part is considered a feature.
9. Bilateral tolerances allow variation in two directions. 10. A free state modifier can only be applied to a tolerance. 11. A free state datum modifier applies to “assists” & “rests”. 12. Virtual condition applies regardless of feature size.
FALSE
TRUE
FALSE
TRUE
TRUE
FALSE
FALSE
TRUE
TRUE
TRUE
FALSE
FALSE
Material Condition Quiz
Internal Features
MMC LMC
External Features
MMC LMC
.890
.885
.895
.890
23.45 +0.05/-0.25
10.75 +0.25/-0
123. 5 +/-0.1
23.45 +0.05/-0.25
10.75 +0/-0.25
123. 5 +/-0.1
Calculate appropriate values
Fill in blanks
10.75 11
23.2 23.5
123.4 123.6
.890 .895
10.75 10.5
23.5 23.2
123.6 123.4
.890 .885
1. Datum target areas are theoretically exact. 2. Datum features are imaginary.
3. Primary datums have only three points of contact. 4. The 6 Degrees of Freedom are U/D, F/A, & C/C. 5. Datum simulators are part of the gage or tool. 6. Datum simulators are used to represent datums.
8. All datum features must be dimensionally stable. 9. Datum planes constrain degrees of freedom. 10. Tertiary datums are not always required.
12. Datums should represent functional features.
Datum Quiz
11. All tooling locators (CD’s) are used as datums.
Questions #1-12 True or False
7. Datums are actual part features.
FALSE
FALSE
FALSE
FALSE
TRUE
TRUE
FALSE
TRUE
TRUE
TRUE
FALSE
TRUE
Datum Quiz
The three planes that make up a basic datum reference frame are called
primary
,secondary
, and tertiary.An unrestrained part will exhibit
3-linear
and3-rotational
degrees of freedom.A planar primary datum plane will restrain
1-linear
and2-rotational
degrees of freedom.
The primary and secondary datum planes together will restrain
five
degrees of freedom.The primary, secondary and tertiary datum planes together will restrain all
six
degrees of freedom.The purpose of a datum reference frame is to
restrain movement
of a part in a gage or tool.
A datum must be
functional
,repeatable
, andcoordinated
. Adatum feature
is an actual feature on a part.A
datum
is a theoretically exact point, axis or plane.A
datum simulator
is a precise surface used to establish a simulated datum.1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Questions #1-10 Fill in blanks (choose from below)
primary
secondary
tertiary
3-rotational
3-linear
2-rotational
datum
three
two
one
six
functional
restrain movement
coordinated
datum simulator
datum feature
repeatable
five
Straightness
andcircularity
are individual line or circular element (2-D) controls.Form Control Quiz
The four form controls are
straightness
,flatness
,circularity
, andcylindricity
.Rule #1 states that unless otherwise specified a feature of size must have
perfect form
at MMC.Flatness
andcylindricity
are surface (3-D) controls.Circularity can be applied to both
straight
andtapered
cylindrical parts.1.
2.
3.
4.
5.
Form controls require a datum reference.
Form controls do not directly control a feature’s size. A feature’s form tolerance must be less than it’s size tolerance.
Flatness controls the orientation of a feature. Size limits implicitly control a feature’s form.