Which of the following is correct?

Question

Question

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BHEL Engineer Trainee Mechanical 24 Aug 2023 Official Paper

Maximum metal limit refers to high limit of size for hole and low limit of size for the shaft.
In interference fit, the largest permissible diameter of the shaft is smaller than the diameter of smallest hole.
In clearance fit, the largest permissible diameter of the shaft is smaller than the diameter of smallest hole.
In clearance fit, the minimum permissible diameter of the shaft exceeds the maximum allowable diameter of the hole.

Answer 1

Concept:

Fit is a relationship that exists between two mating parts a hole and a beam with respect to their dimensional difference before assembly.

There are three types of fits.

Clearance fit:

In this fit the size of the Hole is always greater than the size of the beam. Clearance is the difference between the size of the hole and the size of the beam which is always positive. Here the tolerance zone of the hole will be above the tolerance zone of the beam.
Examples: Slide fit easy sliding fit running fit slack running fit and loose running fit.

Interference fit:

In this fit the size of the Hole is always less than the size of the beam. Interference is the difference between the size of the hole and the size of the beam which is always negative i.e. beam is always larger than the hole size. Here the tolerance zone of the hole will be below the tolerance zone of the beam.
Examples: Shrink fit heavy drive fit and light drive fit.

Transition fit:

It may sometimes provide clearance and sometimes interference. Here the tolerance zones of the hole and beam will overlap each other.
Examples: Tight fit and pushfit wringing fit press fit.