MFGT 124
Solid Design in Manufacturing
GD&T
Professor Joe Greene
CSU, CHICO
Reference: A. Kruilikowski, Effective Training, Inc. Manufacturing
Engineering, 27 (Feb 1994)
MFGT 124
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T
• Topics
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Introduction
History
Feature Control Frames
Material Condition Modifiers
Form Tolerances
Datums
Orientation Tolerances
Runout
Profiles
Position Tolerances
Applications
Copyright 2003 Joseph Greene All Rights Reserved
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Some Greek Letters
• Alpha: 
•
Nu: 
• beta: 
•
xi: 
• gamma: 
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• delta: 
omicron: 
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pi: 
•
rho: 
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sigma: 
•
tau: 
•
upsilon: 
• kappa: 
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phi:
• lamda: 
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chi: 
• mu: 
•
psi: 
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omega:
• epsilon: 
• zeta: 
• eta: 
• theta: 
• iota:

Copyright 2003 Joseph Greene All Rights Reserved
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GD&T
• Introduction
– Drawing quality is an important issue for manufacturing
• Flawed drawings can cause mistakes in the product.
• Poor drawings can easily double manufacturing costs and delivery time.
• Most manufacturing and quality engineers agree that
– 50% of the drawing they see are flawed and
– Require 5 to 10 engineering changes before they define a
manufacturable part.
• Common problems include:
– Undefined reference frames.
– Inadequate or overly restrictive tolerances.
• Frequently, manufacturing makes assumptions about the intent of the design
engineer and problems ensue.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T
• Introduction
– Creating unambiguous part drawings is a demanding thought
process.
• Function of part and process to manufacture and inspect it must be
thoroughly understood and communicated.
– Example,
– Design engineer intends for the part to be inspected with side A
presented to the gage first, with side B as a secondary point of contact,
– Inspector puts Side B to the gage first, and A as secondary point.
– Results:
» Good parts are scrapped since the are measured as out of spec, but
they might be OK.
» Bad parts are shipped off since they pass the inspection.
Copyright 2003 Joseph Greene All Rights Reserved
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• Introduction
GD&T
– Creating detailed GD&T drawings take more time and are more
expensive to make than coordinate dimension drawings.
• Coordinate dimensional drawings are faster to draw and less expensive,
• But have more errors on it and can cause manufacturing problems.
– Example,
• Designer 1 creates drawings with coordinate drawing standards (tolerances
are +/-)
– Time is 20 hours for part A.
– Cost is $50/hr x 20 hours = $1000.
• Designer 2 creates drawing with ASME Y14.5M (GD&T Standards)
– Time is 30 hours for part A.
– Cost is %50/hr x 30 hours = $1500.
• Revisions to correct design problems.
– Paperwork cost range for $500 to $2000 per change.
– If 5 to 10 changes are needed to correct designer 1 then costs of
changes are between $2500 and $20,000.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T vs. Coordinate Measuring
• What is a quality drawing?
– Compare two drawing styles
• Figure 1. GD&T example.
• Figure 2. Coordinate dimensioning example of same part.
– Part straightness
• Both drawings specify a part thickness of 0.25 inches +-0.010”.
• How straight must the part be?
– Fig 1 has GD&T straightness symbol applied to thickness (Area A)
» Symbol on part means that the part must be straight enough to pass
between two parallel plates spaced 0.260”
– Fig 2 has coordinate version says nothing about straightness.
» Part could be within thickness tolerance, yet significantly bowed .
» Note needs to be added to drawing to require straightness.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T vs. Coordinate Measuring
• What is a quality drawing (continued)
– Unwanted tolerance accumulation
• Fig 1 includes several dimensions (B) called basic dimensions which identify exact
locations from which tolerances are specified.
• Fig 2 has no corresponding term and tolerances can accumulate.
– Another note needs to be added “Dimensions are gage dimensions.
– Part inspection Figure 3.
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Different inspection points and procedures can lead to different measurements.
GD&T establishes an order of measurement sequence.
Coordinate measuring does not.
Two inspectors can get totally different results from same part.
GD&T system
– Specifies measurement sequence.
– Parts intended to contact gage are datums. (C Fig 1)
– Geometric tolerance controlling hole locations defines the sequence in which
part surfaces must touch the gage surfaces. (D)
» Reading from left side of positional tolerance callout, the letter sequence
lists the order in which the part touches the gage. A, B, C
• Coordinate measuring system has no equivalent system and as such requires a note.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T vs. Coordinate Measuring
• What is a quality drawing (continued)
– Hole location
• GD&T system (D) contains a symbol (circle with slant in it) that denotes the
shape of the tolerance zone as a diameter.
– Same geometric tolerance includes a circled M symbol (Maximum
material condition) that permits the location tolerance to increase for
larger holes.
• Coordinate measuring system show two ways in which is inadequate:
– Uses square tolerance zones, Fig 4, which allow more tolerance for hole
centers diagonally than vertically or horizontally. Round tolerance zone
is better.
– Requires tolerance zone for hole location to remain fixed in size,
regardless of hole size.
» Small holes have same tolerance zones as larger diameters.
– Notes have to be added for round tolerance.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T vs. Coordinate Measuring
• What is a quality drawing (continued)
– Counterbore location
• GD&T specifies counterbore diameter, depth, and location.
– Includes position symbol under counterbore, E.
» Specifies location relative to small diameter
• Coordinate version only specifies bore diameter and depth, allowing user to
choose between
– Following smaller diameter location, or
– Locating by tolerance dimension for both diameters.
– Note must be added to ensure proper location.
– Equivalent information on Coordinate Measuring drawing
• Fig 6
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T History
• In ancient Egypt,
– Cubit: unit of measure based on length of the Pharaoh’s forearm.
– Span: the distance form the tip of the thumb to the tip of the little
finger,
– Standard meter
• 1789: One- ten millionths of the distance from North Pole to the equator
measured through Paris France.
• 1906: U.S. Prototype Meter number 27-as a “value of 1,553,164.13 times
the wavelength of cadmium red in air, at 760 mm of atmospheric pressure at
15 °C.”
• The continual change in the definition of the measurement is to increase the
accuracy of the meters length.
• The current definition of “the meter is the length of the path traveled by
light in vacuum during a time interval of 1/299,792,458 of a second.”
– The standardizing of dimensioning and tolerancing has paralleled
the development of a more accurate unit of measure
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Standards
• ANSI Y14.5
– The ANSI standard was revised in 1982.
– In 1994, the standard was moved form ANSI to the American Society of
Mechanical Engineers (ASME) and the name changed to ASME Y14.5.
– The standard was also revised into its current form of ASME Y14.5-1994.
• Geometric Dimensioning and Tolerancing (GD&T)
– Establishes the standard by which designers can communicate
• the intended function of the part to the machinist making the part and
• the inspector checking the part.
– This standard lets the designer inform the machinist, toolmaker or fabricator
what are the important features of the design when they are making the part.
– The standard also lets the inspector know what are the important features to
inspect form.
– GD&T uses symbols to communicate the information to those involved in
making the part to eliminate any misunderstanding.
– Word explanations can be confusing especially with the global market and the
translations of words into different languages.
– A simple layout of the symbols used in GD&T can be found in below.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Definitions and Terms
• Feature Control Frames
• Geometric Tolerance Geometric Characteristic Symbol
• The feature control frame helps to organize the various symbols into a
sentence.
• This sentence communicates the information in an organized manner.
– The first is the Geometric Tolerance is the total tolerance band for
that feature.
• This means that it is not a +/- tolerance.
• An example of this is if we have a dimension of 1.00 and a Geometric
tolerance of .005, we can interpret this as 1.000 +/-.0025.
Geometric Characteristic
Symbol
 . 005 
Geometric Tolerance
Figure 3a-1 Simple
Feature Control Frame
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Material Condition Modifiers
• Material Condition Modifiers
– Indicate at what material condition the tolerance is applicable.
– There are three different types of material condition modifiers
• Regardless of Feature Size (RFS)
– Used if the tolerance is to be met at all possible sizes of the feature
to be produced.
– In the current standard, this is assumed if one of the other modifiers
is not specified. In the older standards, the symbol  was placed in
the feature control frame to designate the RFS condition.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Material Condition Modifiers
• Maximum Material Condition (MMC) External
– Indicates that the tolerance given applies only at the maximum amount of
material for that feature. For holes, it is the smallest diameter-Max material
– The key words in this modifier are maximum material.
– When working with external features the MMC is at the largest limit or
maximum amount of material, as shown in Figure 3b.ii.1.
MMC for External Features
• Maximum Material Condition (MMC)- Internal
– When working with internal features the MMC is at the smallest limit, or
maximum amount of material, as shown in Figure 3b.ii.2.
Figure 3b.ii.2 MMC for Internal Feature
– The feature control from the symbol o represents MMC
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Material Condition Modifiers
• Least Material Condition (LMC) External
– Indicates that the tolerance given applies only at the least amount of material for
that feature. For diameters, it is the smallest diameter. For holes, it is the biggest
diameter-Min material
– When working with external features the LMC is at the largest limit or least
amount of material, as shown below.
LMC for External Features
• Least Material Condition (LMC) Internal
– LMC is at the smallest limit, or least amount of material, as shown
LMC for
Features
– The feature control from
theInternal
symbol
 represents LMC
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Form Tolerances
• Form tolerances
– The control the variations of individual features of a part.
• Such features include straightness, flatness, circularity and Cylindricity.
– Form tolerances do not control the relationship between features.
• Straightness
• The straightness tolerance controls all the elements along a
theoretical straight line on a surface or axis.
– The tolerance given for straightness specifics how close to
perfectly straight the feature must be created.
• Depending on the way straightness is defined on the drawing, determines
whether surface elements or an axis is to be controlled.
– The symbol for straightness is 
Straightness Applied to a Surface
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Straightness
• Straightness
Straightness Applied to a Cylinder Surface and Cylinder
• Note that straightness is applied only to the view that it is
defined on a drawing
– The placement of the feature control frame is very important.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Flatness
• Flatness
– A perfectly flat surface must contain all elements in one plane.
– The flatness tolerance establishes a set of parallel planes that must
contain all elements of the surface.
– The flatness tolerance is not used in conjunction with a material
modifier or datum reference it is a stand-alone tolerance.
– The symbol for flatness is .
• Example, gives the different representations of how flatness tolerance is
used in conjunction with a feature control frame.
Two Flatness Tolerance Callout Methods
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Circularity
• Circularity
– Controls the roundness of any feature with circular cross section.
• The circular cross-section must be taken perpendicular to the axis of the
cylinder or cone, or through a common center of a sphere.
• Circularity tolerance is also referred to as the roundness tolerance.
– The symbol for Circularity is c.
• The tolerance zone for a circularity tolerance is bounded by two concentric
circles.
• The tolerance value is determined by the radial distance between the circles,
not the distance between the diameters.
– Example gives a typical call-out for circularity tolerance.
Circularity Form Tolerance Call-Out
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Cylindricity
• Cylindricity
– Controls the surface of a cylinder.
– This tolerance can be applied to a shaft or a hole.
– Cylindricity is identified by a radial tolerance zone that establishes
two perfectly concentric cylinders.
– The surface of the cylinder that the tolerance is applied to must lie
within this tolerance zone.
– The cylindricity tolerance also controls the parallelism of the sides
of the cylinder to prevent the part form being tapered.
– Example gives a typical call-out for cylindricity tolerance.
Cylindricity Form Tolerance Call-Out
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Datums
• Datums
– Theoretically perfect planes, surfaces, points, lines or axes that are
derived form a datum feature.
• Datums are used by designers to specify important features of reference by
which toolmakers and machinists create the part and inspectors check the
part to the print.
• Datum features are actual features of the part, such as a surface, that
establish the datum.
• The feature control frames that define tolerances based on datum features
include datum references.
– Datums are used to establish an inspection point from a surface.
– Checking jigs and fixtures are built based upon datums to inspect
parts.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Datum Identification
• Datum Identification
– A datum feature is identified by using the datum symbol combined
with a datum feature triangle.
Datum Symbol and Application
– A datum target symbol is a circle with a horizontal line across it,
• with the bottom half of the circle used to identify the datum target and the
top is empty except when specifying the diameter of a datum target area.
Datum Target Symbol and Application
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Orientation Tolerances
• Orientation tolerances
– Control the relationship of features to one another.
• Orientation tolerances include parallelism, perpendicularity and angularity.
– Orientation tolerances are datum related and may be applied with
material modifiers MMC or LMC.
– RFS material modifier is always implied unless otherwise stated.
• Parallelism
– Defined as two parallel planes of cylindrical zones that are parallel
to a datum plane where the surface or axis of the feature must lie.
– The symbol for parallelism is 
Parallelism Tolerance Feature Control Frame
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Parallelism
• Parallelism
– There are three main types of parallelism
• call-outs, surface, axis and line.
– When a surface is to be parallel to a datum, the feature control
frame is either connected by a leader to the surface or directly
connected to the extension line of the dimension.
Parallelism Applied to a Surface
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Parallelism
• Parallelism
– When parallelism is applied to an axis the axis of the hole may be
specified within a tolerance zone that is parallel to a given datum.
• The feature control frame is place with the diameter dimension
Parallelism Applied to an Axis
– Parallelism to line elements.
• When it is desirable to control only individual line elements, rather than the
entire surface, the note “EACH ELEMENT” or “EACH RADIAL
ELEMENT”
Parallelism Applied to Line Elements
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Perpendicularity
• Perpendicular geometric tolerance
– Two parallel planes of cylindrical zones that are a basic 90 to a
datum plane where the surface or axis of the feature must lie.
– The symbol for perpendicularity is 
Perpendicular Tolerance Feature Control Frame
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Perpendicularity
• The examples below give different applications of
perpendicularity geometric tolerance.
–
–
–
–
Figure 1 is the application of perpendicularity to a surface.
Figure 2 is the application of perpendicularity to an axis.
Figure 3 is the application of perpendicularity to a center plane.
Figure 4 is the application of perpendicularity of line elements.
Perpendicularity to a Surface
Perpendicularity to an Axis
Perpendicularity to a Center Plane
Perpendicularity to Line Elements
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Angularity
• Angularity geometric tolerance
– A surface, center-plane or axis at a specified angle (other than 90)
form a datum plane or axis.
– The symbol for angularity is 
Angularity Tolerance Feature Control Frame
– Figure 1 the application of angularity to a surface.
– Figure 2 is the application of angularity to an axis.
– Figure 3 is the application of angularity to a center plane.
Angularity to a Surface
Angularity to an Axis
Copyright 2003 Joseph Greene All Rights Reserved
Angularity to a Center Plane
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GD&T Runout Tolerances
• Runout
– Combination of geometric tolerances used to control the
relationship of one or more features of a part to a datum axis.
– The geometric tolerances associated with Runout
• Form, Orientation and Location tolerances.
• The features that may be controlled by Runout are surfaces around, or
perpendicular to, a datum axis.
– There are two types of Runout error,
• Circular Runout and Total-Runout.
– Of these two types of Runout,
– Circular Runout is the less complex.
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Circular Runout
• Circular runout
– Is the error on a single circular element and provides the control of
these elements on a surface.
• The surface must have circular cross sections that are controlled relative to
an axis of rotation.
• Typical surfaces that are controlled by circular runout include
– cylinders, cones, spherical surfaces and flat surfaces.
– The symbol for circular runout is .
Circular Runout Tolerance Feature Control Frame
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Circular Runout
• Circular runout
– The following three examples give some of the different
applications of circular runout.
• Figure 1 gives the application of circular runout as applied to a cylindrical
surface.
• Figure 2 gives the application of circular runout as applied to a noncylindrical feature.
• Figure 3 gives the application of circular runout as applied to face surfaces.
Circular Runout Applied to a Cylindrical Surface
Circular Runout Applied to a Non-Cylindrical Surface
Circular Runout Applied to a Face Surface
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Total Runout
• Total runout
– Is the variation across the entire surface of a cylindrical feature or
perpendicular face surface.
– Total runout is used to control the combined variations of
• circularity, straightness, coaxiality, angularity, taper and profile when
applied to surfaces around and at right angles to a datum axis.
• The symbol for total runout is .
Circular Runout Tolerance Feature
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Total Runout
• Total runout
– Note that total runout cannot be applied to conical or curved
surfaces as can circular runout.
– The following two examples give some of the different
applications of total runout.
• Figure 1 gives the application of total runout as applied to a cylinder.
– The total runout feature control frame, in this figure, references a
compound datum of A and B.
– When checking the feature that references a compound datum both
datum’s A and B must be used together to establish an axis of rotation.
• Figure 2 gives the application of total runout as applied to face surfaces.
Total Runout Applied to a Cylinder with Compound Datum
Total Runout Applied to a Face Surface
Copyright 2003 Joseph Greene All Rights Reserved
34
GD&T Profile Tolerances
• Profile tolerance
– The outline of an object represented either by an external view or
by a cross section through the object.
– Profile tolerances may be used to control form, orientation and
location.
• The manner in which the profile tolerance is applied,
– How it is dimensioned, and
– How datum’s are utilized all effect the level of control desired by using
profile tolerances.
• There are two profile tolerance types,
– Profile of a line and profile of a surface.
– Note: when the profile is other than flat, basic dimensions must be used
to describe the profile.
» A basic dimension is depicted with a box around the dimension and
is considered an exact dimension
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Profile Tolerances
• Profile of a Line
– A two-dimensional cross section tolerance that extends along the
length of the feature.
– The line profile tolerance is used where parts have changing cross
section along their length and do not have to be along the entire
feature.
– The symbol for profile of a line is e.
– Figure shows the feature control frame for profile of a line
geometric tolerance.
Profile of a Line Feature Control Frame
Copyright 2003 Joseph Greene All Rights Reserved
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GD&T Profile Tolerances
• Profile of a Line
– Many automobile companies use an exact profile to gage sheet
metal parts that have changing cross sections.
• The hood of an automobile is a good example of such a cross section that
has a changing profile.
• The profile tolerance is assumed a bilateral tolerance, which is the tolerance
both above and below the true profile line.
• The following examples give usage of the profile of a line tolerance.
Figure. Cross section of a Figure 2. Uses profile of a line to Figure 3 is a special case
simple contour that is
control all around a cross section of using profile of a line
controlled by line profile
for a unilateral
of a wing.
37
tolerance.
specification.
Copyright 2003 Joseph Greene All Rights Reserved
GD&T Profile Tolerances
• Profile of a Surface
– Used to control all the elements of a surface and treats them as a
single entity.
– Profile of a surface, as its definition states, covers all points on a
surface in three dimensions.
– The symbol for profile of a surface is f.
– Figure shows the feature control frame for profile of a line
geometric tolerance.
Profile of a Surface Feature Control Frame
Copyright 2003 Joseph Greene All Rights Reserved
38
GD&T Profile Tolerances
• Profile of a Surface
– As with profile of a line, profile of surface can be measured with a
mater gage to control features of the surface or profile.
– The following examples give usage of the profile of a surface
tolerance.
• Figure 1 is a cross section of a plate with a slot. The slot is controlled by a
profile of a surface tolerance. That means that the depth of the slot as well
as it’s cross sectional profile is controlled.
• Figure 2 uses profile of a surface to control the surface of a part similar to
that seen in figure 3g.i.2.
Figure 1
Copyright 2003 Joseph Greene All Rights Reserved
Figure 2
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GD&T Positional Tolerances
• Position tolerances
– Locate features from datum’s or for establishing coaxiality or symmetry.
• Positional tolerances define
– A zone where the center, axis or center plane of a feature of size is permitted to
vary form true position.
– The true position is the theoretically exact position of the feature.
• Basic dimensions are used to establish the location of the feature in
relationship to datum features.
– When using positional tolerances MMC and LMC must be specified in the
feature control frame after the tolerance otherwise RFS is assumed.
• Positional tolerances are also applied only to features of size; they are not applied to
features of form.
• The format for the positional feature control frame is given below.
Position Tolerancing Feature Control Frame
Copyright 2003 Joseph Greene All Rights Reserved
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History and Current Status of the Plastics Industry