Question

Write a brief note about the type of fits and tolerances in machine elements subject under mechanical engineering

Answer 1

Tolerance

Tolerance is the difference between maximum and minimum dimensions of a component, ie, between upper limit and lower limit. Depending on the type of application, the permissible variation of dimension is set as per available standard grades.

Types of tolerances

1. Unilateral Tolerance: unilateral has tolerance only on one side,

2. Bilateral Tolerance: Tolerance present on both sides of nominal diameter,

Types of Fit

When the mating parts are fit together, There are two ways to represent a system i, Hole basis system ii. shaft basis system

Types of Fit

Clearance Fit In this type of fit, the shaft of largest possible diameter can also be fitted easily even in the hole of smallest possible diameter.

Transition Fit In this case, there will be a clearance between the minimum dimension of the shaft and the minimum dimension of the hole. If we look at the figure carefully, then it is observed that if the shaft dimension is maximum and the hole dimension is minimum then an overlap will result and this creates a certain amount of tightness in the fitting of the shaft inside the hole. Hence, transition fit may have either clearance or overlap in the fit.

Interference Fit

In this case, no matter whatever may be the tolerance level in shaft and the hole, there is always a overlapping of the matting parts. This is known as interference fit. Interference fit is a form of a tight fit.