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Perpendicularity Control
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Define Perpendicularity
Perpendicularity is the condition that results
when a surface, axis, or centerplane is exactly
90 deg to a datum.
A perpendicularity control is a geometric
tolerance that limits the amount a surface, axis,
or centerplane is permitted to vary from being
perpendicular to the datum.
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Perpendicularity Applications1. Perpendicularity applied to a surface.
2. Perpendicularity applied to a planar FOS.
3. Perpendicularity applied to a cylindrical FOS.
Perpendicularity Tolerance Zones
1. Two Parallel Planes
2. A cylinder
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Perpendicularity applied to a
surface
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Interpretations
Tolerance zonetwo parallel planes that are
perpendicular to the datum plane.
Distance between tolerance plane specified
tolerance value. Important criteria all elements of the surface
must be within the tolerance zone.
Perpendicularity tolerance zone limits theflatness of toleranced feature.
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Inspection of perpendicularity
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Perpendicularity control that
contains MMC modifier
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Interpretations
Tolerance zonetwo parallel planes that are
perpendicular to the datum plane.
Distance between tolerance plane specified
tolerance value. The center plane of theActual Mating Envelope
must be within the tolerance zone.
A bonus tolerance is permissible. A fixed gauge may be used to verify the
perpendicularity control.
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Perpendicularity control with
MMC modifier applied to
cylindrical FOS
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Interpretations
Tolerance zonea cylinderthat is perpendicularto the datum plane.
Diameter of the tolerance zone specified
tolerance value. The axis of the diametermust be within the
tolerance zone.
A bonus tolerance is permissible.
A fixed gauge may be used to verify theperpendicularity control.
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Angularity Control
Angularity is the condition of a surface, center
plane, or axis being exactly at the specified
angle.
An angularity control is a geometric tolerance
that limits the amount a surface, center plane, or
axis is permitted to vary from its specified angle.
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Angularity applications
1. Angularity applied to a surface.
2. Angularity applied to a cylindrical FOS.
Angularity tolerance zones
1. Two parallel planes
2. A cylinder
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Angularity applied to a surface.
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Interpretations
Tolerance zonetwo parallel planes that areperpendicular to the datum plane.
Distance between tolerance plane specified
tolerance value. Important criteria all elements of the surface
must be within the tolerance zone.
Tolerance zone is oriented relative to the datum
plane by a basic angle. Angularity tolerance zone limits the flatness of
toleranced feature
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Angularity control applied to a
diametrical FOS
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Interpretations
Tolerance zonea cylinder.
Diameterof the tolerance zone specifiedtolerance value.
The axis of the toleranced feature must be withinthe tolerance zone.
Tolerance zone is oriented relative to the datumplane by a basic angle.
An implied 90 deg basic angle exists in otherdirection
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Inspection of Angularity
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Paral lel ism Con trol
Parallelism is the condition of a surface, center
plane, or axis being exactly parallel to the
datum.
An parallelism control is a geometric tolerance
that limits the amount a surface, center plane, or
axis is permitted to vary from being parallel to
the datum.
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Parallelism Applications
Parallelism applied to a surface.
Parallelism applied to a cylindrical FOS.
Parallelism Tolerance Zones
1. Two parallel planes.
2. A cylinder.
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Parallelism Applied To a Surface
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Interpretations
Tolerance zonetwo parallel planes that areparallel to the datum plane.
Tolerance zone is located within the limits of sizedimension.
Distance between tolerance plane specifiedtolerance value.
Important criteria all elements of the surface
must be within the tolerance zone. Parallelism tolerance zone limits the flatness of
toleranced feature.
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Parallelism Applied to a FOS at
MMC
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Interpretation
Tolerance zonea cylinderthat is parallel to thedatum plane.
Diameter of the tolerance zone specifiedtolerance value.
The axis of the diametermust be within thetolerance zone.
A bonus tolerance is permissible.
A fixed gauge may be used to verify the
parallelism control. Parallelism tolerance zone limits flatness of the
toleranced feature.
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Inspection
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LOCATION
TOLERANCES
Concentricity control
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Concentricity control
This is a type oflocation control.
A median point is the midpoint of a two-point measurement.
A concentricityis the condition where the
median points of all diametrically opposedelements of a cylinder (or a surface ofrevolution) are congruent with the axis ofdatum feature.
A concentricity controlis geometrictolerance that limits the concentricity errorof a part feature.
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Example:
T l f t i it t l
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Tolerance zone for a concentricity controlis three dimensional.
Tolerance zone of concentricity control is acylinder.
The cylinder is coaxial with the datum axis
and diameter of the cylinder equal to theconcentricity control tolerance value.
Median points must lie within thecylindrical tolerance zone.
When using concentricity control, thespecified tolerance and datum referencealways apply on an RFS basis.
Example
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Example
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Concentricity application
Concentricity is used when:
Precise balance of part.
Equal wall thickness.
Equal distribution of mass.
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Inspecting concentricity
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Inspecting Concentricity
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SYMMETRY DEFINITION
Symmetry is the condition where the median
points of all opposed elements of two or more
feature surfaces are congruent with the axis or
centerplane of a datum feature.
A symmetry controlis a geometric tolerance
that limits the symmetry error of a part feature.
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SYMMETRY
ZONE OF TOLERANCE :- TWO PARALLEL PLANES
SYMBOL :-
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A symmetry control may only be applied to part
features that are shown symmetrical to the
datum centerplane.
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The tolerance zone is centered about the datum
centerplane. The width between the planes is
equal to the symmetry control tolerance value.
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When using a symmetry control, the specified
tolerance and the datum references must
always be applied on an RFS basis.
TECHNOTE
The tolerance zone is two parallel planes
centered about a datum axis or centerplane.
The median points of the toleranced feature
must be within the tolerance zone.
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Inspecting Symmetry
When inspecting this part, three separate checks
are required :
size of the
slot,
its Rule #1
boundary and
its symmetry.
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