A countersink drill bit can be secured in any chucked drill motor and will create a recess to allow a countersink bolt to sit flush with the surface of a material. The angle of the countersink screw head determines the angle of the countersink needed to allow the bolt head to sit flush while maintaining full contact with the base material. Using the wrong degree countersink drill bit to countersink a screw leads to poor contact between the two components. This leads to a weak connection between the screw and the base material.
Measuring the degree of the countersink screw head with a bevel degree finder allows the selection of the proper tapered countersink bit. When the inside edges of the bevel finder contact the top of the countersink screw and the length of the countersink screw head taper, the proper angle is shown. Utilizing the bevel degree finder ensures that the connection remains at full strength after the connection has been made. Selecting the type of countersink drill bit for the drilling operation ensures that the bit creates the proper type of hole.
Cross-hole and fluted countersink drill bits both drill through a variety of materials. A cross-hole counter sink drill bit is the most common type of countersink drill bit. The tapered cone of the drill bit reams a correctly sized hole set at a chosen bevel for seating countersink screws at or slightly below the surface of a material. Fluted drill bits use a steeper entry angle for tightly beveled screws or as a starting point for machining of metal base materials.
Tapping and burr removal are two machining process that benefit from using a fluted countersink drill bit. Tapping threads in metal requires an evenly surfaced entry to a hole. Uneven hole entries cause the cutting threads of a starter tap to wander, leading to out-of-level threads, which cause a screw to thread into a metal part at an angle, decreasing the surface contact between a fastener and the base material. Burr removal removes sharp edges from the outside rim of a drilled hole. This increases safety and avoids damaging the screw threads when the fastener is inserted into a drilled hole.
Lubricating both types of countersink drill bits while in use decreases friction at the contact point of the bit taper and the base material. Friction creates heat at the drilling point. Heat causes the cutting edges to dull rapidly during the beveling process.