A drill bushing, also known as a jig bushing, is a tool used in metalworking jigs to guide cutting tools, most commonly drill bits. Other tools that are commonly used in a drill bushing include counterbores, countersinks, and reamers. They are designed to guide, position, and support the cutting tool. In the USA, Customary sized bushings are standardized via ASME B94.33 and metric bushings are standardized via ASME B94.33.1. There are over 50,000 standard configurations of customary sized bushings. Types Drill bushings can generally be classified as: press fit bushings or renewable bushings. Other classification methods include by head type, by use, and by liner type (or lack thereof). Press-fit bushings Press fit are available in two types with liners or without (wearing bushings). Liner bushings, sometimes called master bushings, are permanently installed into the jig and accept liners that can easily be replaced. Press-fit wearing bushings are used in short run applications or in applications where the tolerance on a hole location is so tight that it cannot facilitate the use of a liner bushing. Renewable bushings Renewable bushings are installed in liner bushings. This type of bushing is used in large production runs where a bushing will wear out over time or when multiple renewable bushings are used in one liner to provide various sized holes. There are two types of renewable bushings: fixed and slip. Fixed renewable bushings are used in applications where the liner is meant to be used until it wears out. Slip renewable bushings are designed to be interchangeable with a given sized liner so that two different sized slip renewable bushings can be used in one liner bushing. This facilitates the ability to do multiple machining operations that require different inner diameter (ID) bushings, such as drilling and reaming. They usually have knurled heads so they can be easily removed. Renewable bushings must be secured in their liner bushing, otherwise the tool can cause it to spin, which rapidly wears out the liner, or chips can force the bushing out of the liner. There are many different types of locking systems for renewable bushings. One system is a dog, which is a collar that is pressed over the head of the bushing and has a long tail. The tail may be bent at the end so it can lock around the edge of the jig plate or it may be left straight if