Limits and Fits Mechanical Calculator
Concept Procedure Quick Reference

Limits and Fits Mechanical Calculator

Use to design fits and limits.


Ribbon: Design tab Power Transmission panel Limits/Fits Calculator

The Limits and Fits Mechanical calculator takes recommendations from ISO 286 or ANSI B4.1. The option to select a standard is available within the More Options area. (To display the More Options area, click More in the lower right corner of the Calculation tab.) Each standard has its own profile and the units of the nominal diameter and deviations are millimeters for ISO and inches for ANSI.


Tolerance Zones

Specify the limits and fits. Selected fit is displayed in a graphic form.

Fit Type

Select Clearance, Transition, or Interference.

Preferred Fits

Select 1 of the predefined Fits. The list is dynamically updated when the Fit Type is changed. The Limits graph is dynamically updated to display the selected fit.


Select the limit letter and number. The Limits graph is dynamically updated to display the selected Limits. If you manually enter any letter or number, the Fit Type and Preferred Fits pull-down lists are disabled. When you click the Fit Type and Preferred Fits drop-down arrows, you enable these selections and Limits entries are reset to default values.

Limits are defined by a letter and a number. Capitol letters are used for holes, and lower case letters are used for shafts.

The letter is the Fundamental Deviation from the basic size. It is the maximum size or upper tolerance of the feature.

The number is the Standard Tolerance Grade. It is the size of the tolerance zone. Subtract the Standard Tolerance Grade from the Fundamental deviation to determine the minimum size or lower tolerance of the limit.

Limits graph

Displays all available hole and shaft tolerance classes for the entered nominal diameter and tolerance grade. You can see currently selected tolerance class, displayed in a hidden line. Pause the cursor over each fit symbol to see the information about any fit deviations, which belong to the selected tolerance class. Click a tolerance class to change it.

The Zero line is displayed. The fit parameters are dimensioned to show the tolerance zone dependencies clearly. The dimensions that join the center of the tolerance zones can have a value of less than zero. Using this technique, you can design the transition fit with respect to the maximum center value. It defines the Interference fit (negative) or Clearance fit (positive).



To display the Results area on the right side of the Calculation tab, double-click the double line on the right or click the chevron.

The area displays numerical values for the tolerances. Click Calculate to calculate the values.

The following items are displayed in the Results pane:

Toolbar buttons