Fit dimensions

Fit dimensions define the tolerance specification for the proper fit between holes and shafts. In QY CAD, you can specify that a dimension is a fit dimension when you set the Dimension Type=Class on the command bar for the dimension. For more information, see Set the dimension display type

Because the tolerance specification for the proper fit between holes and shafts is such a common and critical aspect in the design and manufacture of parts, international standards bodies established rule-based systems of tolerances for the Limits and Fits of holes and shafts. The terms hole and shaft also can refer to the space between two parallel faces of any part, such as the width of a slot, the thickness of a key, etc. Only distance dimensions are covered by the standards; the standards do not apply to angular dimensions.

You can use the Type list on the command bar to specify the fit dimension display type.

You can specify tolerance formatting options for fit dimensions by editing the dimension properties or by defining it in the dimension style. Refer to the following options on the Text tab, in the Tolerance Text group:

Hole/Shaft

Three separator types are available to specify the layout of class fit hole/shaft dimensions with tolerance.

Use these options	For this layout
Separator	Vertical
Space	Vertical
Slash	Horizontal

Position

Use these options	To get this layout
Bottom	Tolerance aligned to the bottom of the dimension text.
Center	Tolerance center-aligned with the dimension text.
Top	Tolerance aligned to the top of the dimension text.

Align to

The following options are available to specify alignment of the upper tolerance value with the lower tolerance value:

• Decimal point

• Sign

Use tolerance text size for combined tolerance text values

When upper and lower tolerance values are the same, specifies that the combined values are displayed using the tolerance text size entered in the Size box.

Example:

Inhibit display of 0.0 values for automatic fit tolerances

Controls whether zero value tolerances are displayed or hidden.

You also can set this option for an individual dimension using the Properties command, or you can set it for all dimensions using the Styles command.

Three ASCII text files are available that provide support for ANSI and ISO fit dimension standards. You can use these text files to automatically define the limit or fit for dimensions with different class sizes.

• SE-LimitsAndFitsTableANSIinch.txt

• SE-LimitsAndFitsTableANSIMetric.txt

• SE-LimitsAndFitsTableISO.txt

By default, the files are located in the QY CAD Preferences folder. You can instruct QY CAD to look for these files in a different folder, including a folder on another machine on the network using the File Locations tab in the QY CAD Options dialog box.