Table of Contents Table of Contents .......................................................................................................................................... 1 Form Checks: ................................................................................................................................................. 2 Circularity (Roundness)*: ...................................................................................................................... 2 Cylindricity: ........................................................................................................................................... 4 Straightness*:........................................................................................................................................ 5 Flatness: ................................................................................................................................................ 7 Orientation Checks: ...................................................................................................................................... 8 Angularity, Perpendicularity and Parallelism: ....................................................................................... 8 Location Checks: ......................................................................................................................................... 10 Surface Profile: .................................................................................................................................... 10 Composite Surface Profile Check: ....................................................................................................... 13 Line Profile Check*: ............................................................................................................................. 15 True Position Check: ........................................................................................................................... 17 Composite True Position Check: ......................................................................................................... 20 Circular Runout Check*: ...................................................................................................................... 21 Total Runout Check: ............................................................................................................................ 24 Concentricity*: .................................................................................................................................... 26 GD&T Dimension Tolerances ...................................................................................................................... 28 ***checks marked with a star indicate that they are cross‐section checks Form Checks: Form checks take the measurements provided to the check and compare them directly to the designated elements or axis or center plane and evaluate the extent of the deviation from that. Datums are therefore not required (expect for circularity). Form annotations can be added to CAD Faces, SA objects or directly to points defining geometry. Circularity (Roundness)*: Circularity is a cross‐sectional check therefore measurements must be grouped accordingly. The check is evaluated in either of two ways, along the axis of a circle or cylinder normal vector or through the center point of a sphere (circularity for a sphere is not yet supported in SA). The tolerance establishes the minimum distance between two concentric circles containing the measurements of that part at the cross section location. Circularity Evaluation Process within SA: 1. The actual feature type is first established (circle or cylinder) based on the nominal type (feature to which the annotation is attached). 2. This feature type is fit to the entire data set to establish the direction vector 3. Cross sections are established along this direction vector and the data is divided into groups based upon their position along this vector. 4. A plane is fit to the first point in each cross section group (using the actual feature direction vector) and then the points are projected onto that plane 5. Bounding circles are then established on the plane containing the data and the distance between these is used to evaluate the cross section 6. The check returns the worst of the cross section results. To check the circularity of a part do the following: 1. Import or build the desired annotation a. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type b. In the Feature Checks section enter the desired tolerance c. Select the nominal CAD faces, SA objects, or measured points to evaluate, if measurements have already been taken. This will add the annotation to the selected object with the specified tolerance and view. If you select the SA Objects (fit to points) option, it will also construct a nominal object, associate the points to the check and evaluate the check. ***Remember that the object type you use (circle or cylinder) will greatly influence the nominal vector direction. 2. Build Feature Checks from the Annotations 3. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 4. Measure your part within the designated cross sections using geometry triggers or another appropriate measurement technique. Cylindricity: Cylindricity checks ensure that all the specified points are the same distance from a common axis. The tolerance establishes the minimum distance between two concentric cylinders containing the measurements of that part. Cylindricity Evaluation Process within SA: 1. Two coaxial cylinders are built bounding the extents of the data. 2. The cylinders are allowed to freely rotate to establish the minimum distance between them while still containing the data. To check the Cylindricity of a part do the following: 1. Import or Build the desired annotation a. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type b. In the Feature Checks section enter the desired tolerance c. Select the nominal CAD faces, SA objects, or measured points to evaluate, if measurements have already been taken. This will add the annotation to the selected object with the specified tolerance and view. If you select the SA Objects (fit to points) option, it will also construct a nominal object, associate the points to the check and evaluate the check. 2. Build Feature Checks from the Annotations 3. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 4. Measure your part within the designated cross sections. Straightness*: Straightness checks ensure that all the measured points are within a specified proximity to a straight line within a cross section. SA currently only supports straightness checks for lines and cylinders (axis). Evaluated as a zone in which the median line must lie. Straightness is a cross‐
sectional check so measurements must be grouped accordingly. Straightness Evaluation Process within SA: 1. The direction vector is established for the measured feature (line or cylinder) 2. Cross sections are established along this direction vector and the data is divided into groups based upon their position along this vector. 3. A plane is fit to the first point in each cross section group (using the actual feature direction vector) and then the points are projected onto that plane 4. Median points are established for each cross section, either directly (for lines) or by fitting circles to the data (cylinder) 5. These median points are then compared to the nominal axis line. 6. The check returns the worst of the cross section results. To check the Straightness of a part do the following: 1. Import or Build the desired annotation a. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type b. In the Feature Checks section enter the desired tolerance c. Select the nominal CAD faces, SA objects, or measured points to evaluate, if measurements have already been taken. This will add the annotation to the selected object with the specified tolerance and view. If you select the SA Objects (fit to points) option, it will also construct a nominal object, associate the points to the check and evaluate the check. 2. Build Feature Checks from the Annotations 3. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 4. Measure your part within the designated cross sections. Flatness: Flatness checks ensure that all the specified points lie approximately on a common plane. The tolerance establishes the minimum distance between two parallel planes containing the measurements of the part and is evaluated as the distance between those two planes. Flatness Evaluation Process within SA: 1. Two parallel planes are built bounding the extents of the data. 2. These planes are allowed to freely rotate to establish the minimum distance between them while still containing the data. To check the Flatness of a part do the following: 1. Import or build the desired annotation a. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type b. In the Feature Checks section enter the desired tolerance c. Select the nominal CAD faces, SA objects, or measured points to evaluate, if measurements have already been taken. This will add the annotation to the selected object with the specified tolerance and view. If you select the SA Objects (fit to points) option, it will also construct a nominal object, associate the points to the check and evaluate the check. 2. Build Feature Checks from the Annotations 3. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 4. Measure your part within the designated cross sections. Orientation Checks: Orientation checks require at least a single datum for evaluation. The measurements of the datum are first aligned to the datum features and then the measurements of the check feature are evaluated relative to that alignment. Perpendicularity and Parallelism are special cases of an angularity check where the angle is either 90 or 0 degrees respectively and the steps are therefore exactly the same in creation, evaluation and tolerancing. For simplicity we will only refer to angularity here. Orientation annotations can be added to CAD Faces, SA objects or directly to points defining geometry. Angularity, Perpendicularity and Parallelism: Angularity checks ensure that all the specified points lie at approximately a specified angle relative to the datum features. The tolerance can be established in either of 2 ways: A. The minimum distance between two parallel planes at the specified angle containing the measurements of the feature. B. The minimum diameter of a cylindrical zone at the specified angle containing the measurements of the feature. To check the Angularity of a feature on a part do the following: 1. Import or build the desired annotation: a. Build the datum annotations: i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. Click on the Datum button and select the nominal CAD faces, SA objects, or measured points to be used to define the datum(s). b. Build the Angularity, Perpendicularity or Parallelism check: i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. In the Feature Checks section enter the desired tolerance and datums to be referenced by the check. iii. Select the nominal CAD faces, SA objects, or measured points to evaluate, if measurements have already been taken. This will add the annotation to the selected object with the specified tolerance and view. If you select the SA Objects (fit to points) option, it will also construct a nominal object, associate the points to the check and evaluate the check. 2. Build Feature Checks from the Annotations 3. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 4. Measure your part within the designated cross sections. Location Checks: Location checks are the heart of GD&T analysis and provide the greatest flexibility and most complexity. A simple example of how to build a check of each type is provided here but greater detail should be obtained from the standard directly. Location checks can be evaluate excluding datums entirely or by including as many datums as are needed to fully constrain the model. Because of the complexity and variety of applications for these checks annotations can only be added directly to CAD Faces or SA objects and the SA Objects (fit to points) option is disabled. Surface Profile: Profile checks provide the ability to evaluate size, form, orientation and location. Currently this check is only supported for surfaces not SA objects. An inner and outer profile boundary is derived from the nominal features included in the check. This tolerance boundary can either be symmetrical or asymmetrical based upon the tolerance designation within the annotation. The nominal feature is first aligned to the datum structure which can include any number of datums to fully constrain the part. Measurements are then fit to the features to minimize the point deviations as allowed by the remaining degrees of freedom. The measured deviations are then compared to the tolerance boundary structure and the part evaluated accordingly. Surface Profile Evaluation Process within SA: 1. An inner and outer tolerance boundary is established based upon the tolerance for the considered features (which can be designated asymmetrical). 2. These feature are allowed to freely rotate based on the datum constraints to minimize the maximum and minimum point deviations. 3. The extent of the max and min deviation is used to establish the measured profile deviation and compared to the tolerance zone. To check the Profile of a feature on a part do the following: 1. Import or build the desired annotation: a. Build the datum annotations if desired (not including datums does not use the current alignment for evaluation but allows the part to move without constraint to fit the data): i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. Click on the Datum button and select the nominal CAD faces, SA objects, or measured points to be used to define the datum. b. Build the surface profile check: i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. In the Feature Checks section enter the desired tolerance and datums to be referenced by the check. iii. Select the nominal CAD faces or SA objects to be evaluated. This will add the annotation to the selected object with the specified tolerance and view. 2. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 3. Measure your part and the evaluation will update automatically if the report bar is visible. The distance between two parallel surface features containing the measured data and oriented at the specified angle to the datum: Composite Surface Profile Check: Composite Surface Profile Checks provide a means to evaluate the position of a pattern of features and combine that with a tighter evaluation of the form of that profile relative a less restricted set of datum constraints all within a single check. Each segment of the composite check evaluated using the same tolerance constraints as described for a single profile check but with the following additional freedoms: Compound verses Composite Position: What makes Composite Surface Profile checks unique from two separate position checks is that composite checks provide a greater degree of freedom in the lower segment check than would be allowed through a secondary check. Take the following check for example: The part is first fit to Datum A, B, and C, which fully locks down all degrees of rotation and translation and the upper segment of the control frame is evaluated. The pattern is then completely released to translate freely and rotate within the degrees of freedom not locked down by datum A to fit the nominal pattern. They key here is that translation is completely unconstrained. Now consider the second case. In this case we have two independent checks which can either be evaluated individually or together returning a single pass/fail result. In this case the upper segment is evaluated, and then in the second check the part is fit to datum A. This locks down both the translation and rotation of the part. In this case the difference is slight. The part is limited in its ability to move toward and away from datum A. The difference is more apparent with two datums in the lower segment. The part is both constrained in position to datum A and B. This restriction in translation and rotation and only allows the part to slide in a straight line perpendicular to the datums to fit the data. As a composite check this is not the case. The part is still free to translate to fit the pattern, only its rotation is constrained by A and B. Line Profile Check*: Line profile is much like surface profile except that it is a 2D check. The tolerance zone is normal to the true profile of the feature at each line element. This can be a useful addition if you want to evaluate a single portion of a surface at a location. It considers a set of curves which lie on a surface and evaluates the curves individually. 
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Line profile currently only works with CAD faces, not SA objects You must associate a direction object (SA object) with the line profile annotation before creating the feature check object ‐ this direction object defines the direction along which the data is divided into cross‐sections for analysis o If you associate multiple direction objects, it uses the average of their direction Line Profile annotations can be imported with CAD but a direction object (SA object) must be associated with the annotation to be evaluated. If you create a line profile annotation using the GD&T toolbar, you'll get an additional selection stage after picking the CAD faces allowing you to pick the direction object(s) Line Profile Evaluation Process within SA: 1. The direction vector for analysis is established from the direction object chosen. 2. Cross sections are established along this direction vector and the data is divided into groups based upon their position along this vector and the cross section criteria set. 3. A plane is fit to the first point in each cross section group (using the actual feature direction vector) and then the points are projected onto that plane 4. An inner and outer tolerance boundary is established based upon the tolerance for the considered features. 5. These feature are allowed to freely rotate based on the datum constraints to minimize the maximum and minimum point deviations. 6. The extent of the max and min deviation is used to establish the measured profile deviation and compared to the tolerance zone. To check the Line Profile of a feature on a part do the following: 1. Import or build the desired annotation: a. Build the datum annotations if desired (not including datums does not use the current alignment for evaluation but allows the part to move without constraint to fit the data): i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. Click on the Datum button and select the nominal CAD faces, SA objects, or measured points to be used to define the datum. b. Build the line profile check: i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. In the Feature Checks section enter the desired tolerance and datums to be referenced by the check. iii. Select the nominal CAD faces to be evaluated and the direction object to be used. This will add the annotation to the selected object with the specified tolerance and view. 2. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 3. Measure your part and the evaluation will update automatically if the report bar is visible. True Position Check: Position checks provide the ability to evaluate size, orientation and location. The number of datums specified, the number of measurements and the type of feature determines the way in which the evaluation is conducted. Position checks can be divided into 2 types:  The zone within which the center, axis, or center plane of a features is permitted to very from the nominal  A boundary (MMC or LMC basis) defined as a virtual condition located at the theoretical position that may not be violated. Position checks are checks that establish the position of a measured feature and compare it to the true position of the nominal feature, evaluating if it is within the specified tolerance. Position checks can be established for many other datum features such as slots, lines, and surfaces. However, position checks are evaluated either relative to a center point, an axis or a plane to establish position. Cylinders are a complex feature than can evaluated in either of 4 ways. Within SA this evaluation method is assigned automatically based upon the number of points measured but can also be specified. Cylindrical Features: Projected 2D evaluations: 1. Trans Axis Center Position Measurements: A single point measurement, or the average point from a set of measurements, is projected along the nominal axis of the cylindrical feature and the distance between this single point and the nominal point evaluated as a straight line 2D distance on the nominal planar surface. 2. Center and Diameter at Nominal Direction: Measurements of the diameter a cylindrical feature are projected along the nominal axis to the nominal planar surface. A circle is fit to these measurements and its center point defined. The straight line 2D distance between this measured center point and the nominal center is evaluated. Axis or 3D evaluations: 3. Center and Surface Axis Measurements: Two or more points are used to define an axis, assumed to be taken at various distances along its length. The diameter of a cylinder along the nominal axis containing the measured axis definition is used to evaluate the position of the feature. 4. Full Cylinder Evaluation: When a minimum of 10 points are obtained a full cylinder fit can be performed. Measurements are assumed to be taken from the extents of the cylindrical feature. A measured cylinder is established and its axis is compared to the nominal axis for evaluation. **Currently the extent of the Measurements determines the length of the axis used in the comparison to the nominal for both axis or 3D evaluations. Datum Designation: Position Checks must have a datum associated to be correctly evaluated.  When specifying a MMC or LMC position tolerance a second annotation must also be included on the same feature to specify the nominal dimension. If you do not an error “No size tolerances defined for feature” will be seen. This second annotation will be automatically recognized and included in the evaluation.  Coaxial and coplanar datums can be specified with a dash as in: A|B‐C|D We do not offer a "coaxiality" check specifically but rather support its evaluation through a positional tolerance. In evaluating the True Position of a feature relative to a single datum axis you are essentially checking the coaxiality of that feature relative to that datum. Composite True Position Check: Composite True Position Checks provide a means to evaluate the position of a pattern of features and combine that with a tighter evaluation of the position of each feature relative to each other feature within a single check. Compound verses Composite Position: What makes Composite True Position checks unique from two separate position checks is that composite checks provide a greater degree of freedom in the lower segment check than would be allowed through a secondary check. Consider a composite check like this: The part is first fit to Datum A, B, and C, which fully locks down all degrees of rotation and translation and the upper segment of the control frame is evaluated. The pattern is then completely released to translate freely and rotate within the degrees of freedom not locked down by datum A to fit the nominal pattern. They key here is that translation is completely unconstrained. Now consider the second case. In this case we have two independent checks which can either be evaluated individually or together returning a single pass/fail result. In this case the upper segment is evaluated, and then in the second check the part is fit to datum A. This locks down both the translation and rotation of the part. In this case the difference is slight. The part is limited in its ability to move toward and away from datum A. The difference is more apparent with two datums in the lower segment. The part is both constrained in position to datum A and B. This restriction in translation and rotation and only allows the part to slide in a straight line perpendicular to the datums to fit the data. As a composite check this is not the case. The part is still free to translate to fit the pattern, only its rotation is constrained by A and B. SA Restrictions: 
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We do not currently support additional tiers beyond 2 (additional tiers were added in 2009) The lower tier must specify the same ordering of datums as the upper segment. So you cannot have A|B|C in the upper tier and then B in the lower tier. Circular Runout Check*: Circular runout is a cross section check that is used to evaluate features relative to a datum axis therefore measurements must be grouped accordingly. It establishes a width between two concentric circles contain the measurements of the feature. In doing so it controls variations in both circularity and coaxiality around the datum axis. 
For features at 90 angle to the datum axis runout controls the circular elements of a planar surface or “Wabble”… evaluation of these feature are not currently supported in SA. Circular Runout Evaluation Process within SA: 1. The actual feature type is first established (circle or cylinder) based on the nominal type (feature to which the annotation is attached). 2. This feature type is fit to the entire data set to establish the direction vector 3. Cross sections are established along this direction vector and the data is divided into groups based upon their position along this vector. 4. A plane is fit to the first point in each cross section group (using the actual feature direction vector) and then the points are projected onto that plane 5. Bounding circles centered on the datum axis are then established on the plane containing the data and the distance between these is used to evaluate the cross section 6. The check returns the worst of the cross section results. To check the Runout of a part do the following: 1. Import or build the desired annotation: a. Build the datum annotations if desired (not including datums does not use the current alignment for evaluation but allows the part to move without constraint to fit the data): i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. Click on the Datum button and select the nominal CAD faces, SA objects, or measured points to be used to define the datum. b. Build the Total Runout check: i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. In the Feature Checks section enter the desired tolerance and datums to be referenced by the check. iii. Select the nominal CAD faces or SA objects to be used for the feature check. This will add the annotation to the selected object with the specified tolerance and view. 2. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 3. Measure your part within the designated cross sections. Clay sent me the below. This is from the standard and shows an example where a circular runout check is done on a feature where that same feature is also a datum in the check. So, it looks like that is valid after all. Since the circular runout check requires measurements in cross‐sections, you have two choices for doing this in SA. Either just make your measurements for both the datum and circular runout in cross‐sections and measure once (which goes along with the SA assumption that you don't want to measure the same feature twice), or if you really want different measurements for each, then measure twice and manually associate after the fact. It would be interesting to do some testing and see what you get when you measure a set of good cross sections and use those for both the datum and check vs. having more 'random' measurements for the datum and using the good cross section measurements for the check. Total Runout Check: Total runout is used to evaluate features across their length relative to a datum axis or axis of rotation. Therefore 1 or more datums are required. It provides a cumulative evaluation of deviations in circularity, straightness, coaxiality, taper, profile, etc. It establishes a revolved tolerance zone around the features using the datum axis and establishes point deviation relative to this zone. For features at 90 angle to the datum axis runout controls the circular elements of a planar surface or “Wabble”. 
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Currently SA only supports runout for cylinders and cylindrical surface (10 points minimum). It does not support features at 90 angle to the datum. Asymmetrical tolerance zones are not permitted. Total Runout does not support SA objects fit to points. Total Runout Evaluation Process within SA: 1. Measurements of the datum are fit to the datum feature to establish a nominal axis. 2. A boundary regions is established based upon the tolerance for the considered features. 3. These features are allowed to freely translate along the nominal axis based on the datum constraints to minimize the maximum and minimum point deviations. 4. The extent of the max and min deviation is used to establish the measured profile deviation and compared to the tolerance zone. To check the Total Runout of a part do the following: 4. Import or build the desired annotation: a. Build the datum annotations if desired (not including datums does not use the current alignment for evaluation but allows the part to move without constraint to fit the data): i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. Click on the Datum button and select the nominal CAD faces, SA objects, or measured points to be used to define the datum. b. Build the Total Runout check: i. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type ii. In the Feature Checks section enter the desired tolerance and datums to be referenced by the check. iii. Select the nominal CAD faces or SA objects to be used for the feature check. This will add the annotation to the selected object with the specified tolerance and view. 5. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 6. Measure your part and the evaluation will update automatically if the report bar is visible. Concentricity*: Concentricity requires a single datum to be defined. The measurements of the datum are first aligned to this datum and then the measurements of the check feature are evaluated relative to this datum by establishing a median point for each cross section and comparing its position relative to the axis of the datum feature. Concentricity Evaluation Process within SA: 1. The measurements of the datum are aligned to the datum feature which orients the nominal feature and the measurements of it. 2. The actual feature type is established (circle or cylinder) based on the nominal type (feature to which the annotation is attached). 3. This feature type is fit to the entire data set to establish the direction vector for this measured feature. 4. Cross sections are established along this direction vector and the data is divided into groups based upon the distance of each point along this direction vector and the cross section width definition. 5. The data in each cross section is evaluated independently. A circle is fit to the data in each group using the datum direction axis and the center or “medial” point established. 6. The distance of each median point from the datum axis is used for the evaluation. To check the concentricity of a part do the following: 1. Import or build the desired annotations a. In the Creation Options section of the GD&T Toolbar set the desired annotation View and Feature Type b. In the Feature Checks section enter the desired tolerance c. Select the nominal CAD faces or SA objects. This will add the annotation to the selected object with the specified tolerance and view. If you select the SA Objects (fit to points) option, it will also construct a nominal object, associate the points to the check and evaluate the check. ***Remember that the object type you use (circle or cylinder) will greatly influence the nominal vector direction. 2. Build Feature Checks from the Annotations 3. Begin trapping to the Feature Check by either right‐clicking on the check in the tree and selecting Tap Measurements from an Instrument or by double‐clicking on the check within the Inspection tab of the Toolkit. 4. Measure your part within the designated cross sections using geometry triggers or another appropriate measurement technique. GD&T Dimension Tolerances