ABOUT INTRODUCTION OR TOLERANCES

WHAT IS INTRODUCTION OR TOLERANCES?

• It is essential that the manufacturing of the machine element has to be done as per the specified dimensions (sizes), specified geometry (shapes), and specified surface finish.
• However, it is not possible to manufacture a machine element to the exact dimensions (sizes) and exact geometry (shapes) specified by the designer. There will be variations.
• Therefore, the design engineer has to make the provision for some permissible variations in dimensions (sizes) as well as geometry (shapes) of the machine element.
  

        Methods of Making Provisions of Permissible Variations in Dimensions and                  Geometry :

1. Dimensional Tolerances :

           The provision of the permissible variations in the dimensions (sizes) of the machine                         element  or component is made with the help of dimensional tolerances.

     2. Geometrical Tolerances :

          The provision of the permissible variations in the geometry (shapes) of the machine                          element  or component is made with the help of geometrical tolerances.

     TOLERANCES (DIMENSIONAL TOLERANCES)

• It is not possible to manufacture a machine element or component to the exact specified dimensions. Therefore, some permissible range is given for the dimension between maximum and minimum limits so that the operator can produce the machine element or component with the dimension laying between the two limits. This permissible range of the dimension is called tolerance.
• Tolerance (dimensional tolerance) :

          Tolerance can be defined as the permissible variation in the dimension of the component. It            is the difference between the maximum and minimum size limits of the component.