# FITS AND TOLERANCE CALCULATOR

Fits and tolerance calculator for shaft and hole tolerance calculation according to ISO 286-1 and ANSI B4.2 metric standards . The schematic representation of the fit is also drawn by tolerance calculator.

The tolerances defined in ISO 286-1 are applicable to size range from 0 mm to 3150 mm but there are exceptional cases defined in the standard which depends on tolerance selection. If the calculation results given by the tolerance calculator are "---", then this means the input parameters are not applicable according to ISO standard.

### Fits and Tolerance Calculator:

 INPUT PARAMETERS Parameter Value Unit Nominal Size mm Hole Tolerance A B C CD D E EF F FG G H JS J K M N P R S T U V X Y Z ZA ZB ZC 01 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 --- Shaft Tolerance a b c cd d e ef f fg g h js j k m n p r s t u v x y z za zb zc 01 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ---

Note : Use dot "." as decimal separator.

 RESULTS HOLE Parameter Value Unit Designation --- --- Hole Upper Deviation --- μm (0.001mm) Hole Lower Deviation --- μm (0.001mm) Maximum Hole Size --- mm Minimum Hole Size --- mm SHAFT Parameter Value Unit Designation --- --- Shaft Upper Deviation --- μm (0.001mm) Shaft Lower Deviation --- μm (0.001mm) Maximum Shaft Size --- mm Minimum Shaft Size --- mm FIT Parameter Value Unit Designation --- --- Fit Type --- --- Maximum Clearance --- μm (0.001mm) Minimum Clearance --- μm (0.001mm)

### Basic terminology for tolerances and deviations:

Designation of the tolerance class: The tolerance class shall be designated by the combination of an upper-case letter(s) for holes and lowercase letters for shafts identifying the fundamental deviation and by the number representing the standard tolerance grade. For example H7 tolerance class for holes and h7 tolerance class for shafts.

Nominal size: The size of a feature of perfect form as defined by the technical drawing.

Deviation: The difference between a size and the corresponding nominal size.

Hole: Internal feature of size of a workpiece, including internal features of size which are not cylindrical.

Shaft: External feature of size of a workpiece, including external features of size which are not cylindrical .

Upper deviation: The difference between the maximum limiting size and the corresponding nominal size of a feature.

Lower deviation: The difference between the minimum limiting size and the corresponding nominal size of a feature.

Limits of Size: Extreme permissible sizes of a feature of size.

Upper limit of size: Largest permissible size of a feature of size.

Lower limit of size: Smallest permissible size of a feature of size.

Tolerance: The difference between the maximum and minimum size limits of a part.

Fit: Relationship between an external feature of size and an internal feature of size (the hole and shaft of the same type) which are to be assembled.

Clearance: The difference between the size of the hole and the size of the shaft when the diameter of the shaft is smaller than the diameter of the hole.

Interference: The difference before mating between the size of the hole and the size of the shaft when the diameter of the shaft is larger than the diameter of the hole.

Clearance Fit: A fit type where clearance exists between assembled parts under all tolerance conditions.

Interference Fit: A fit type where interference exists between assembled parts under all tolerance conditions.

Transition Fit: A fit type where clearance or interference can exist between assembled parts depending on tolerance conditions.

GD&T A means of dimensioning and tolerancing a part with respect to relationship and function of that part. GD&T is used to define how a part feature relates the other part features in the same part or in a mating part; it’s a way to dimension and tolerance with respect to part’s function, the way it works.

### What is ISO system for tolerances?

The need for limits and fits for machined workpieces was brought about mainly by the requirement for interchangeability between mass produced parts. In order that fit function could be satisfied, it was found sufficient to manufacture a given workpiece so that its size lay within two permissible limits, i.e. a tolerance, this being the variation in size acceptable in manufacture while ensuring the functional fit requirements of the product. Similarly, where a specific fit condition is required between mating features of two different workpieces, it is necessary to ascribe an allowance, either positive or negative, to the nominal size to achieve the required clearance or interference.

ISO 286 establishes a system for tolerances to be used for linear sizes of features of cylinder and two parallel opposite surfaces. It provides a standardized selection of tolerance classes for general purposes from amongst the numerous possibilities. The main intention of this system is the fulfilment of the function fit.

### Reference:

• ISO 286-1 (2010) Geometrical product specifications (GPS) - ISO code system for tolerances on linear sizes - Part 1: Basis of tolerances, deviations and fits
• ISO 286-2 (2010) Geometrical product specifications (GPS) - ISO code system for tolerances on linear sizes - Part 2: Tables of standard tolerance classes and limit deviations for holes and shafts
• ANSI/ASME B4.2 (1978) Preferred Metric Limits and Fits