Q1: The machanism involved in the removal of metal in drilling operation is by

ANS:D - both 'b' & 'c'

1. Shearing:
   • Shearing is the primary mechanism involved in the removal of metal during drilling operations.
   • When a drill bit rotates and applies pressure against the material being drilled, it cuts into the material by shearing off small chips or particles.
   • The cutting edges of the drill bit penetrate the material and create shear forces that cause the material to deform and eventually separate from the workpiece in the form of chips.
   • Shearing is particularly effective in materials like metal, where the material's strength allows it to be sliced or sheared off cleanly.
2. Extrusion/Compression:
   • While shearing is the primary mechanism, extrusion and compression also play secondary roles in drilling operations.
   • Extrusion occurs when the material being drilled is subjected to high pressure from the drill bit, causing it to flow or deform plastically. This deformation can lead to material being pushed outwards from the hole, especially in softer materials.
   • Compression involves the application of compressive forces to the material. In drilling, these forces can cause localized compression around the drill bit, particularly at the drill bit's tip. This compression can help weaken the material, making it easier for the shear forces to remove it.
   • However, compared to shearing, extrusion and compression typically contribute less to the overall material removal process in drilling operations, especially in metals where shearing is the dominant mechanism.

In summary, while shearing is the primary mechanism involved in the removal of metal during drilling operations, extrusion and compression also play secondary roles, particularly in softer materials or specific drilling conditions. However, shearing remains the most significant process in metal removal during drilling.