## ISO Dimension Tolerances

Note: This only applies to location dimensions created by a GD&T Selection.

ISO tolerances will have an alphanumeric label instead of normal plus and minus tolerance values. The labels will be displayed as "H7", "h7" or "G9" for example as shown below.

Example of ISO Tolerances in a PC-DMIS graphic

The following is based on ISO Standard 268-1, ISO system of limits and fits.

The letter ("H", "h", "g", etc.) indicates the tolerance class. It is case-sensitive: capitol letters indicate holes or other internal shapes, while lower-case letters indicate stems or other external shapes.

The number indicates the grade of the tolerance.

For the ISO Tolerances to work in Planner (or PC-DMIS), the tolerance values must be set up in a CSV (Comma-Separated Value) file.

The following two lines show a part of a sample CSV file and corresponds to the first half of the '7' column in Table 6 of ISO 286-2: 1988 (E) which defines the values for an H7 tolerance:

H7, 0, 3, 6, 10, 18, 30, 50, 80, 120, 180, 250, 315, 400, 500

0.010, 0, 0.012, 0, 0.015, 0, 0.018, 0, 0.021, 0, 0.025, 0, 0.030, 0, 0.035, 0, 0.040, 0, 0.046, 0, 0.052, 0, 0.057, 0, 0.063, 0

The initial entry on the first line, H7, defines the type of tolerance these two lines will apply to. The values in these two lines will only be applied to tolerances that have H7 in them.

The rest of that line defines size categories. The first size category will be for dimensions greater than 0 and less than or equal to 3. The second is for greater than 3 and less than or equal to 6. The third is for larger than 6 and less than or equal to 10, etc.

The next line gives the tolerance values that match up to the size categories in line 1. The plus/minus tolerances for the first size category is +0.010/-0. The second is +0.012/-0. The third is +0.015/-0, etc.

For PC-DMIS or PC-DMIS Planner, to use a tolerance CSV file, you need to select that CSV file from the GD&T Selection Settings dialog. Use the ISO Dimensions Tolerance File combo box from the GD&T Selection Settings Dialog to choose the CSV file that you wish to use as shown below.

GD&T Selection Settings dialog

Access this dialog by selecting Edit | Preferences | CAD GD&T Selection menu in PC-DMIS, or through the Edit | Setup | GD&T Selection menu in Planner.

For more detailed information on ISO Dimension and Tolerance standards, visit the ISO web site.