Question

Write a short report (not exceeding 2 page excluding the reference list, based on APA Style (Double spacing)) regarding Shaft and Hole Tolerances and Fits. You need to explain engineering fits and how to determine fits in your own words. (Minimum 3 references). 2 pages report includes introduction, main body and conclusion.

Answer 1

Limits:

The maximum and minimum permissible sizes within which two actual sizes of a component lies are called limits.

Functional Requirement, Interchangeability and production are necessary to consider in limits choosing.

Tolerance:

Tolerance is the amount by which the given dimension is permitted to vary and is equal to the algebraic difference between upper and lower deviation

The difference between the maximum limit of size and minimum limit of size is called tolerance.

Two Types of Tolerances:

1. Unilateral Tolerances: When the two limit dimension are only on one side of the nominal Size, (either above or below), the tolerance are said to be unilateral.

Example: Shaft and bearing used for mating parts

2. Bilateral tolerance:

When the two limit dimensions are above and below nominal Size (on either Side of the nominal Size), the tolerance is Said to be bilateral.

Example: Thickness of flywheel and used for non-mating parts.

Allowance:

It is defined as the difference between the maximum material limits of the components. It is taken as the minimum Clearance between the mating parts.

Clearance:

It is the difference between Sizes of the hole before assembly and difference is positive

Minimum interference = minimum Size of the hole - maximum size of the shaft

Maximum interference = maximum Size of the hole – minimum Size of the shaft

Fit:

Fit is defined as the relationship between hole and shaft during assembly.

When two parts are to be assembled, the relationship resulting from the difference between their Sizes before assembly.

Classification of fit

1. Depending on actual limits of hole or shaft.

(i) Clearance fit: if the lower limit of the hole is larger than the upper limit of the shaft.

(ii) Interference fit: If the maximum size of the hole is smaller than the minimum Size of the shaft, then, the force has to be applied to make the assembly.

lii) Transition fit:

This type of fit appears when there is an overlap in the tolerance zones.

If Upper limit of one of the component is lying in between the lower limit and upper limit of other Components is called a transition fit.