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Dimensioning your drawing

Adding geometric tolerances

Geometric tolerances indicate the maximum allowable variations in the geometry defined by a drawing. progeCAD draws geometric tolerances using a feature control frame, which is a rectangle divided into compartments.

Each feature control frame consists of at least two compartments. The first compartment contains a geometric tolerance symbol that indicates the geometric characteristic to which the tolerance is applied, such as location, orientation, or form. For example, a form tolerance may indicate the flatness or roundness of a surface. The geometric tolerance symbols and their characteristics are shown in the following table.

Geometric tolerance symbols

Symbol

Characteristic

Type

 

Position

Location

 

Concentricity or coaxiality

Location

 

Symmetry

Location

 

Parallelism

Orientation

 

Perpendicularity

Orientation

 

Angularity

Orientation

 

Cylindricity

Form

 

Flatness

Form

 

Circularity or roundness

Form

 

Straightness

Form

 

Profile of a surface

Profile

 

Profile of a line

Profile

 

Circular runout

Runout

 

Total runout

Runout

The second compartment contains the tolerance value. When appropriate, the tolerance value is preceded by a diameter symbol and followed by a material condition symbol. The material conditions apply to features that can vary in size. The material condition symbols and their meanings are shown in the following table.

Material conditions

Symbol

Definition

 

At maximum material condition (MMC), a feature contains the maximum amount of material stated in the limits.

 

At least material condition (LMC), a feature contains the minimum amount of material stated in the limits.

 

Regardless of feature size (RFS) indicates that the feature can be any size within the stated limits.

  1. The tolerance value can then be followed by primary, secondary, and tertiary datum reference letters, along with the material conditions of each datum. Datum reference letters are generally used as reference tolerances to one of up to three perpendicular planes from which a measurement is made, although datum reference letters can also indicate an exact point or axis.
    2.  
    1. Geometric characteristic symbol.
    2. Diameter symbol.
    3. Tolerance value.
    1. Material condition symbol.
    2. Datum reference.
  2. When two tolerances apply to the same geometry, you can also add a composite tolerance consisting of a primary tolerance value followed by a secondary tolerance value. To make a tolerance even more specific, it can also contain a projected tolerance consisting of a height value followed by a projected tolerance symbol. For example, you can use a projected tolerance to indicate the perpendicularity of an embedded part.
To add a geometric tolerance
  1. Do one of the following:
  2. Choose Dimension > Tolerance.
  3. On the Dimension toolbar, click the Tolerance tool (
    4. ).
  • Type tolerance and then press Enter.
  • To display the geometric tolerance symbols, on the first line, click the Sym box.
  • Click to select a geometric tolerance symbol.
  • Under Tolerance 1, click the Dia box to add a diameter symbol.
  • In the field, type the first tolerance value.
  • To display the material condition symbols, click the M.C. box.
  • Click to select a material condition.
  • Under Tolerance 2, repeat steps 4 through 7 to add a secondary tolerance value, if appropriate.
  • Under Datum 1, type the primary datum reference letter.
  • To display the material condition symbols, click the M.C. box.
  • Click to select a material condition.
  • Repeat steps 9 through 11 to add secondary and tertiary datum, if appropriate.
  • In the second row, repeat steps 2 through 12 to add composite tolerances, if appropriate.
  • In the Height box, type a projected tolerance zone height value, if appropriate.
  • To insert a projected tolerance zone symbol, click the Projected Tolerance Zone box, if appropriate.
  • Click OK.
  • In the drawing, specify the location of the feature frame.
    •  
    1.  
    1. Use this row to include composite tolerances.
    2. Type a projected tolerance height value.
    3. Type a datum identifier.
    4. Click to include a projected tolerance symbol.
    5. Click to select the material condition symbol for tertiary data.
    6. Type the tertiary datum reference letter.
    7. Click to select the material condition symbol for secondary datum.
    8. Type the secondary datum reference letter.
    9. Click to select the material condition symbol for primary datum.
    1. Type the primary datum reference letter.
    2. Click to select the material condition symbol for the second tolerance value.
    3. Type the second tolerance value.
    4. Click to include a diameter symbol for the second tolerance value.
    5. Click to select the material condition symbol for the first tolerance value.
    6. Type the first tolerance value.
    7. Click to include a diameter symbol for the first tolerance value.
    8. Click to select a geometric tolerance symbol.