What is the purpose of a countersink bit?

The purpose of a countersink bit is to set the head of a screw below the surface. This is achieved by creating a conical-shaped recess in the material, allowing the screw head to sit flush with or slightly below the surface. This is especially important in applications where a smooth finish is desired, such as in woodworking or in surfaces where fixtures need to be level without any protruding hardware.

Countersink bits not only help in achieving an aesthetically pleasing finish but also provide a stronger hold for the screw since the taper allows the screw to seat more securely. This technique helps to prevent damage to the material being fastened, as screws that are not countersunk can create points of weakness or splintering.

The other options describe different types of drilling tasks or tools that do not have the function of countersinking. For example, drilling wide holes for bolts or creating large openings in concrete would use different varieties of bits designed for those specific purposes, such as spade bits or masonry bits, respectively, while drilling straight holes in metal typically uses twist drills.