The mode of deformation of the metal during spinning is bending and stretching.

Bending:
During the spinning process, a flat metal disc or blank is clamped onto a rotating mandrel and pressure is applied to the outer edge of the blank using a spinning tool. This causes the metal to deform and bend into the desired shape. Bending typically occurs at the edges of the blank where the tool contacts the metal.

Stretching:
As the spinning tool applies pressure to the blank, the metal is also stretched. This stretching occurs in the radial direction, causing the blank to thin out and elongate. It is a result of the metal being forced to conform to the shape of the mandrel and the spinning tool.

Combined Effect:
The bending and stretching actions are interrelated during the spinning process. As the metal is bent, it also stretches to accommodate the curvature of the mandrel and the spinning tool. Similarly, as the metal is stretched, it also bends to follow the shape that is being formed.

Importance of Bending and Stretching:
Bending and stretching are crucial for achieving the desired shape and dimensions in spun parts. The bending action allows for the formation of complex curves and contours, while stretching ensures that the metal is evenly distributed and does not thin out excessively.

Advantages of Spinning:
Spinning offers several advantages over other metal forming processes. It is a cost-effective method for producing seamless, hollow parts with high strength and structural integrity. The process is highly flexible and can be used to create a wide range of shapes and sizes. Spinning also allows for efficient material usage, as it minimizes waste compared to other machining processes.

Applications of Spinning:
Spinning is commonly used in the manufacturing of products such as kitchen utensils, lighting fixtures, musical instruments, and aerospace components. It is particularly suited for producing parts with symmetrical shapes and smooth surfaces.

In conclusion, the mode of deformation of the metal during spinning is a combination of bending and stretching. These actions are essential for achieving the desired shape and dimensions in spun parts and are key factors in the success and versatility of the spinning process.