1、Countersunk Drill: Suitable for countersunk drills, the countersunk bolts or screws are flush with the surface of the surrounding material or lower than the surface of the surrounding material when put in the hole 2、Drill Hole Removal: These countersinks can be used to remove burrs left by drilling or tapping operations, thereby improving the finish and removing any dangerous pointed edges 3、3 Main Elements: Engineering drills has 3 main elements for making countersinks, pilot drill, countersink and countersink collar (sliding up and down) 4、One Operation: Pilot holes, through holes and countersinks can be drilled in one operation, suitable for the most commonly used size screws 5、With Collars: The collars on these twist drills allow you to change the depth of the pilot hole and the depth of the countersink 6、Wide Application: Suitable for woodworking applications that require flat head screw head finishes, tapered drills have greater gripping power than standard drills