A countersink bit creates an area in the wood that matches the countersunk shape of the screw head. This shape allows the screw to contact the wood with an equal amount of force. This creates a strong joint between the screw and the wood.
What is the purpose of a countersink bit?
Countersinks are mainly used for countersinking drill holes, countersinking screws and deburring. Countersinking widens the drill hole and facilitates subsequent tapping. When countersinking screws, space is created for the screw head so that it closes with the surface of the workpiece.
Can you countersink without bit?
If you are out on the job and find yourself without a countersink bit, this method will work in a pinch. Take your Philips Head bit and place it in the spot where the screw will go. Start the drill and move it around in a circular motion, widening the hole as you go until you get the desired size.