In a shaft-hole system, the dimensions with tolerances (in mm) are as follows:

\(Shaft: \;\;\phi\; 20_{-x}^{+x} \;\;\;\;\;\;Hole: \;\;\phi\; 20_{-y}^{-0.03}\)

where both x and y are positive real numbers. Which one of the following will provide an interference fit?

This question was previously asked in

GATE PI 2018 Official Paper

Option 4 : x = 0.02, y = 0.035

**Concept:**

- Interference fit: Interference is the
**difference between the size of the hole and the size of the shaft which is always negative**i.e. shaft is always larger than the hole size. Here, the tolerance zone of the hole will be below the tolerance zone of the shaft. - Examples: Shrink fit, heavy drive fit and light drive fit.

**Calculation:**

Minimum Interference = Upper Limit of Hole - Lower Limit of Shaft

Min I = ULH - LLS = (20 - 0.03) - (20 - x)

For option 1: x = 0.05, y = 0.040 ⇒ Min I = (20 - 0.03) - (20 - 0.05) = 0.02

For option 2: x = 0.04, y = 0.035 ⇒ Min I = (20 - 0.03) - (20 - 0.04) = 0.01

For option 3: x = 0.04, y = 0.032 ⇒ Min I = (20 - 0.03) - (20 - 0.04) = 0.01

For option 4: x = 0.02, y = 0.035 ⇒ Min I = (20 - 0.03) - (20 - 0.02) = **- 0.01**

**A negative difference has come only for option 4.**

**It shows that the shaft-hole will have an interference fit for this dimension with specified tolerance.**

__Additional Information__

- Clearance fit: Clearance is the difference between the size of the hole and the size of the shaft which is always positive. Here the tolerance zone of the hole will be above the tolerance zone of the shaft.
- Examples: Slide fit, easy sliding fit, running fit, slack running fit and loose running fit.

- Transition fit: It may sometimes provide clearance and sometimes interference. Here the tolerance zones of the hole and shaft will overlap each other.
- Examples: Tight fit and push-fit, wringing fit, press fit.

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