Correct option is D
In workshop practice, a bell punch is a hand tool specifically designed for locating and marking the centre of circular or cylindrical objects, such as round bars or shafts. It has a conical recess at its tip, which fits over the curved surface of the round workpiece. When the bell punch is tapped lightly with a hammer, it produces a clear center mark exactly on the axis of the round end.
Mathematically and geometrically, the tool works by ensuring symmetry about the circular cross-section. Since the bell punch encloses the circumference uniformly, the point of impact coincides with the geometric centre of the circle. This makes it much more accurate than using a regular center punch directly on a curved surface, where slipping is likely.
Bell punches are commonly used before operations such as drilling, turning, or facing, where precise centering is critical. For flat surfaces, a center punch is preferred, but for round ends, the bell punch is the correct and safest choice.
