What is Tolerance

Definition of Tolerance: 

The components are manufactured that all lie in between maximum and minimum limits.

The basic dimensions are called the normal or basic size while the difference between the two limits is called permissible tolerance.

Tolerance is defined as the permissible variation in the dimension of the components.

Tolerance has two systems of specifications :
  • Unilateral
  • Bilateral
In unilateral one tolerance is zero while others take care of all permissible variation in the basic size.

In bilateral tolerance, the two tolerance are often equal.

In machine design, there are two basic systems for giving
tolerance to the shaft or hole :
  • Hole basis system
  • Shaft basis system
According to the Bureau of Indian Standards, tolerance is specified by an alphabet, capital or small followed by number Example: G8 or h6

There are eighteen grades of tolerances: IT1, IT2 up to IT18

The letters of symbol IT stand for INTERNATIONAL TOLERANCE GRADE