A drill bushing is a cylindrical metal guide piece used to direct the approach and retreat angle of a drill bit. They look like thick bolts or metal slugs with a hole running through their center. The bit passes through the length of the drill bushing on its way to the location of the new hole. Corresponding bits and bushings are made to exact dimensions for a snug fit. For applications where precision drilling is paramount — such as in manufacturing, machining and metal working — drill bushings are often used.
The job of the bushing is to ensure that a drill bit travels a uniform path and forms holes with identical dimensions. Bushing-regulated bits are often used by large-scale firms to reduce human influence and error in the manufacturing process. Demanding conditions inside a factory can be hard on the drilling machinery and its operators. Heavily used drill bits heat up and may begin to wobble unless a bushing holds them steady. Bits and bushings are commonly coated in grease to reduce friction and prevent the overheating that leads to damage.
Mounting jigs are commonly employed to secure drill bushings to a work surface. Adjustable clamps lock the jig on once the bushing is inserted. Custom drill bushing jigs are often included with gun modification kits. The jig simply snaps onto the gun to guide the drill operator to the precise spot for the hole.
Holes in manufactured metal materials are regularly cleared and threaded for bolt fasteners using drill bushings. Specialized counterbore and countersink drill bits are used to create the clean openings that improve bolt effectiveness and joint strength. A bolt driven into a precisely prepared hole can typically be lowered until it is flush with the material. Tight connections like these increase the durability of manufactured products. The guidance provided by a drill bushing makes it possible to create uniform holes for strong connections.
Warped or cracked drill bushings allow the bit to wobble which may cause it to travel offline. Older well-used bushings require an occasional inspection to make sure they are not showing damage. Uneven gaps between the drill bit and the bushing are indicators of a worn passageway through the drill bushing. It is difficult to fully repair and return a drill bushing to the original manufactured standard. For this reason, most broken drill bushings are discarded and replaced with new identical pieces.