Question

The holes through which the fish plates are fitted to join the rails are oval in shape because:

1. Bolts are oval in shape.
2. To allow the movement of rails in the direction of length due to change in temperature.
3. To make the fitting easy and tight.
4. Only oval shape holes are possible.

Answer 1

Friction between the wheels and coaches of the train has increased in temperature thus the expansion of the metal bar takes place.
Due to the thermal expansion of metals the oval shape makes some space between the rails that even when expansion takes place in metal there will be no overlapping and bends.

Complete step by step solution:
We will first discuss the fish plates and then the reason for holes having oval shape.
A fish plate is a metal bar that is bolted to the ends of two rails to join them together in a track.
We generally use four bolts in order to make the joins because fishplates are long in lengths and to avoid any large vibration on the track. When four bolts are used they are tightly packed leaving very less noise behind.
When a large number of trains run on the tracks every day, higher friction is developed on the fish plates which give rise to increase in temperature of the track and thus cause thermal expansion of the fishplates; therefore if the holes of the fish plates are oblong in shape or oval there will be much space left for the rails to expand easily without causing any bend or overlapping of the rails.

Thus, option 2 is correct.

Note: We have different types of fish plates used on Indian rail tracks such as standard fishplate which are in use these days, Joggled fish plates used for connecting rail tracks together of same or different sections to provide emergency repairs to broken welded rail or fractured rail sections, special fish plates the track portion to be detected has to be electrically isolated from adjoining rails so as to block the track circuit current.