ME 493 – In-class GDT Exercises

For the part shown in the figure:

Specify the following tolerances on the part drawing on the back of this sheet. Do not place any dimensions other than the ones stated in the questions. You can make a copy of the back page and do the exercises on two pages if you like.

  1. Define plane P1 as Datum-A.
  2. Define slot S1 as Datum-B.
  3. Define plane P2 as Datum-C.
  4. Make Datum-A feature flat to within 0.02 mm.
  5. Make Datum-B perpendicular to Datum-A to within 0.05 mm.
  6. Make Datum-C perpendicular to Datum-A and Datum-B to within 0.1 mm.
  7. Specify the size limits of hole H1 to be 20 +/-0.02 mm.
  8. Specify the size of slot S1 to 76.00 – 76.15 mm.
  9. Specify the size of holes H2 to be 12.00 – 12.25 mm.
  10. Specify hole H1 to be parallel to plane P1. Use a tolerance value of 0.1 mm.
  11. Specify H1 to have a cylindricity of 0.08 mm
  12. Specify the entire profile-1 to have a profile of a surface tolerance of 0.75 mm with respect to datum-A and datum-B and datum-C
  13. Specify a circularity of 0.03 for H1

ME 493 – In class GDT exercise. Consider the turning support

Specify the following labels and tolerances.

  1. Define P1 as datum-A.
  2. Define S1 as datum-B.
  3. Define P2 as datum-C.
  4. Make datum-A feature flat to 0.02 mm.
  5. Make datum-B feature perpendicular to datum-A feature to within 0.05 mm.
  6. Make datum-C feature perpendicular to datum-A and datum-B to within 0.1 mm.
  7. Specify the size limits of H1 to 20 +/-0.02 mm.
  8. Specify the size of S1 to 76.00 – 76.15 mm.
  9. Specify the size of H2 to 12.00 – 12.25 mm.
  10. Specify H1 to be parallel and located to P1 and aligned with S1. Use a tolerance value of 0.1 mm.
  11. Control H2 to be perpendicular to P1 and aligned to S1. Use a tolerance value of 0.75 mm.
  12. Control the orientation of H1 to be more precisely parallel to P1. Use a tolerance value of 0.06 mm.
  13. Control the size and location of Prof1 to be parallel to and located to the P1 and aligned with (centered to) S1. Use a tolerance value of 1 mm.
  14. Refine the size and orientation precision of Prof1 relative to P1 using a tolerance value of 0.5 mm.
  15. Specify a plate thickness tolerance of 0.5 mm using short-hand profile tolerance specification using any of the two parallel faces as implicit datum.
  16. Control the location and orientation of the H2 holes with respect to P1 and slot center plane S1.

Meaning of Form Tolerances

Flatness Tolerance: Show the specification for flatness with a 1 mm tolerance value. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Straightness of Axis Tolerance: Show the specification for straightness of an axis with a 1 mm tolerance value. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Circularity Tolerance: Show the specification for circularity of a circular cross-section with a 1 mm tolerance value. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Cylindricity Tolerance: Show the specification for cylindricity of a cylindrical feature with a 1 mm tolerance value. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Profile of a surface tolerance (w/o datums): Show the specification for profile of a surface specification with a 1 mm tolerance value. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Meaning of Orientation Tolerances

Perpendicularity: Show the specification for perpendicularity of a subject feature plane with respect to a planar datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Perpendicularity: Show the specification for perpendicularity of a subject feature cylinder (axis) with respect to a planar datum feature. Draw the theoretical gage for the specification. How do you establish the axis of an imperfect cylindrical feature? How do you test a feature against this gage?

Parallelness: Show the specification for parallelness of a subject feature plane with respect to a planar datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Parallelness: Show the specification for parallelness of a subject cylindrical feature with respect to a planar datum feature. Draw the theoretical gage for the specification. How do you establish the axis of an imperfect cylinder? How do you test a feature against this gage?

Parallelness: Show the specification for parallelness of a subject cylindrical feature (axis) with respect to a cylindrical (axis) datum feature. Draw the theoretical gage for the specification. How do you establish the axis of an imperfect cylinder? How do you test a feature against this gage?

Angularity: Show the specification for angularity of a subject feature cylinder (axis) with respect to a planar datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Profile of a surface (with orientation datum): Show the specification for profile of a surface tolerance to be oriented relative to a planar datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Meaning of Position Tolerances

Position of a cylindrical surface: Show the specification for position of a subject axis with respect to a primary planar datum feature, a secondary planar datum feature, and a tertiary planar datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Position of a cylindrical surface: Show the specification for position of a subject axis with respect to a primary planar datum feature, a secondary center plane datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Position of a cylindrical surface: Show the specification for position of a subject axis with respect to a primary planar datum feature, a secondary axis datum feature, and a tertiary center plane datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Position of a pattern of cylindrical surfaces: Show the specification for position of a pattern of subject axes with respect to a primary planar datum feature, a secondary planar datum feature, and a tertiary planar datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Position of a width feature (center plane) : Show the specification for position of a subject center plane feature with respect to a primary planar datum feature and a secondary center plane datum feature. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Note: We cannot control the orientation of a feature pattern using orientation-control specifications (parallelness, perpendicularity, angularity). To do that, we need to use a composite position tolerance.

Composite position tolerance – single-segment: Controls the orientation of a pattern of cylindrical features: Show the specification for position of a pattern of subject axes with respect to a primary planar datum feature, a secondary planar datum feature, and a tertiary planar datum feature. Use a position tolerance value of 0.1 mm. Modify the position specification to control the orientation of the pattern with respect to the primary datum only with 0.05 mm tolerance value. Draw the theoretical gage for the lower orientation-control specification. How do you test a feature against this gage?

Composite position tolerance – multiple-segment: Controls the position of a pattern of cylindrical features with finer accuracy relative to some datum features: Show the specification for position of a pattern of subject axes with respect to a primary planar datum feature, a secondary planar datum feature, and a tertiary planar datum feature. Use a position tolerance value of 0.1 mm. Modify the position specification to control the position of the pattern with respect to the primary datum and the secondary datum with 0.05 mm tolerance value. Draw the theoretical gage for the lower position-control specification. How do you test a feature against this gage?

Meaning of Runout Tolerances

Circular runout (radial): Using circular runout tolerance, control the coaxiality of a shaft surface carrying a gear with respect to the features that define the axis of rotation of the gear. Circular runout controls the radial wobble of the shaft surface elements with respect to the axis of rotation. Draw the theoretical gage for the specification. How do you test a feature against this gage? What physical set up can be used to check circular runout?

Circular runout (axial): Using circular runout tolerance, control the perpendicularity of a shaft shoulder element with respect to the features that define the axis of rotation of the gear. Circular runout controls axial wobble of the shoulder elements as the shaft rotates. Draw the theoretical gage for the specification. How do you test a feature against this gage? What physical set up can be used to check circular runout?

Total runout (radial): Using total runout tolerance, control the coaxiality of a rollercylindrical surface with respect to the features that define the axis of rotation. Total runout controls the radial wobble of the entire surface relative to the axis of rotation. Draw the theoretical gage for the specification. How do you test a feature against this gage? What physical set up can be used to check circular runout?

Meaning of Profile Tolerances

Profile-of-a-surface: Control the form, size, orientation , and location of a profile surface with respect to a primary datum plane, secondary datum slot (center plane), and a tertiary datum plane. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Composite profile-of-a-surface tolerance (single segment): Control the form, size, orientation , and location of a profile surface with respect to a primary datum plane, secondary datum slot (center plane), and a tertiary datum plane. Modify the profile statement to control its size and orientation with finer control relative to the primary datum plane and the secondary center plane datum and the tertiary datum plane.

Composite profile-of-a-surface tolerance (multiple segment): Control the form, size, orientation , and location of a profile surface with respect to a primary datum plane, secondary datum slot (center plane), and a tertiary datum plane. Modify the profile statement to control its size and location with finer control relative to the primary datum plane and the secondary center plane datum.

Profile-of-a-line: After applying a profile-of-a-surface statement to control the entire surface, control the size of at each cross-section with a finer profile-of-a-line control statement. Draw the theoretical gage for the specification. How do you test a feature against this gage?

Default tolerances

  • Profile-of-a-surface as the default tolerance control statement
  • Default tolerances represent the minimum expected accuracy
  • Default tolerances should be easily held with good manufacturing practices and workmanship

Profile of a surface tolerance as a substitute for +/- dimensions (except for features-of-size)

Unequally distributed profile tolerance zones

Features-of-size:

  • Cylindrical (hole or boss) or pattern of them (axes)
  • Width (slot or rail) or patterns of them (center planes)
  • Spherical
  • Partial cylindrical or width features with sufficient surface area to fit a mating feature without falling out

Maximum material condition (MMC): the limit of size where the feature has the maximum material (largest shafts, smallest holes)

Least material condition (LMC): the limit of size where the feature has the least material (smallest shaft, largest hole)

Axis control versus surface control

The following specifications could be applied to control axes of cylindrical features:

  • Straightness of an axis
  • Orientation of an axis
  • Position of an axis or a pattern of axes

The following specifications could be applied to control center plane of width features:

  • Flatness of center plane
  • Orientation of center plane
  • Position of a center plane or a pattern of center planes

The meaning of axis control tolerances when tolerance value is followed by m

Without any other symbols in the tolerance control statement, the tolerance statements are called to be regardless of feature size (RFS). For RFS statements, the subject feature is the axis or center plane of the feature.

When the maximum material modifier m follows the straightness, the intent is to directly control the surface of the feature not its axis. The combination of feature size and its deformation (bending) must not cause the surface to exceed the allowed boundary. The tolerance zone is now a boundary rather than a small zone. For a shaft, the boundary is a tube. The size of the tube is equal to the shaft largest size plus the applicable straightness tolerance. [Examples]. For a hole, the boundary is a bar. The size of the bar is equal to the hole’s smallest size minus the applicable straightness tolerance. [Examples]. Flatness is similar but instead of tubes and bars there would be slots and rails. [Examples]

m qualified specifications are very important is fit assurance. m qualified specifications can be verified by physical gaging

When the maximum material modifier m follows the orientation tolerances, the combination of feature size and its orientation (and deformation) must not cause the surface to exceed the allowed boundary. The boundary replaces the small tolerance zones but it maintains its orientation to the datum simulator of the gage. For a shaft, the boundary is a tube. The size of the tube is equal to the shaft largest size plus the applicable straightness tolerance. [Examples]. For a hole, the boundary is a bar. The size of the bar is equal to the hole’s smallest size minus the applicable straightness tolerance. [Examples]. Slot and rail feature zones are similar but instead of tubes and bars there would be slots and rails. [Examples]

When the maximum material modifier m follows the position tolerances, the combination of feature size and its position (plus deformation and orientation) must not cause the surface to exceed the allowed boundary. The boundary replaces the small tolerance zones but it maintains its orientation to the datum simulators of the gage. For a shaft, the boundary is a tube. The size of the tube is equal to the shaft largest size plus the applicable straightness tolerance. [Examples]. For a hole, the boundary is a bar. The size of the bar is equal to the hole’s smallest size minus the applicable straightness tolerance. [Examples]. Slot and rail feature zones are similar but instead of tubes and bars there would be slots and rails. [Examples]

There is also al modifier. The use of l modifier is limited in application.

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