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A drill bushing, also known as a jig bushing, is a
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).
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 
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 it can butt up against another object. Another option to keep the renewable bushing from rotating is to pin it, either by putting a pin in the renewable bushing and a hole in the liner or vice versa. A more complicated version uses a hole in the bushing collar and a pin with a head; the head on the pin holds the edge of the collar down, but for removal the bushing can be rotated so that the hole lines up with the pin.
A common problem encountered is when two or more holes are too close for independent standard bushings. In this case one large renewable bushing can be made with two (or more) holes in the proper location (the first example in the image). Another possibility is to make a custom bushing with an
tool
A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates ba ...
used in metalworking
Metalworking is the process of shaping and reshaping metals to create useful objects, parts, assemblies, and large scale structures. As a term it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale ...
jig
The jig ( ga, port, gd, port-cruinn) is a form of lively folk dance in compound metre, as well as the accompanying dance tune. It is most associated with Irish music and dance. It first gained popularity in 16th-century Ireland and parts of ...
s to guide cutting tool
In the context of machining, a cutting tool or cutter is typically a hardened metal tool that is used to cut, shape, and remove material from a workpiece by means of machining tools as well as abrasive tools by way of shear deformation. The major ...
s, most commonly drill bit
Drill bits are cutting tools used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order ...
s. Other tools that are commonly used in a drill bushing include counterbore
A counterbore (symbol: ⌴) is a cylindrical flat-bottomed hole that enlarges another coaxial hole, or the tool used to create that feature. A counterbore hole is typically used when a fastener, such as a socket head cap screw or fillister head ...
s, countersink
A countersink (symbol: ⌵) is a conical hole cut into a manufactured object, or the cutter used to cut such a hole. A common use is to allow the head of a countersunk bolt, screw or rivet, when placed in the hole, to sit flush with or below the ...
s, and reamer
A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precisio ...
s. They are designed to guide, position, and support the cutting tool..
In the USA, Customary sized bushings are standardized via ASME
The American Society of Mechanical Engineers (ASME) is an American professional association that, in its own words, "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via "continuing ...
B94.33 and metric
Metric or metrical may refer to:
* Metric system, an internationally adopted decimal system of measurement
* An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement
Mathematics
In mathem ...
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
Machining is a process in which a material (often metal) is cut to a desired final shape and size by a controlled material-removal process. The processes that have this common theme are collectively called subtractive manufacturing, which utilizes ...
operations that require different inner diameter (ID) bushings, such as drilling and reaming. They usually have knurled
Knurling is a manufacturing process, typically conducted on a lathe, whereby a pattern of straight, angled or crossed lines is rolled into the material.
Etymology
The terms ''knurl'' and ''knurled'' are from an earlier ''knur'' ‘knot in wo ...
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 it can butt up against another object. Another option to keep the renewable bushing from rotating is to pin it, either by putting a pin in the renewable bushing and a hole in the liner or vice versa. A more complicated version uses a hole in the bushing collar and a pin with a head; the head on the pin holds the edge of the collar down, but for removal the bushing can be rotated so that the hole lines up with the pin.
Specification
Customary bushings are specified using the following specification layout: :ID-Type-OD-Length Where the ID is specified as a decimal, drill letter size, drill number size, or fraction; the OD is aninteger
An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign (−1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...
that relates to a multiple of a th of an inch (); the length is an integer that relates to a multiple of a th of an inch. The lengths of press-fit bushings are standardized to typical jig plate thicknesses: , , , , 1 , , and inch (, , , , , and ). The letter "U" is used after the OD number to designate that extra stock should be left on the OD for grinding
Grind is the cross-sectional shape of a blade.
Grind, grinds, or grinding may also refer to:
Grinding action
* Grinding (abrasive cutting), a method of crafting
* Grinding (dance), suggestive club dancing
* Grinding (video gaming), repetitive and ...
to size. The type is a letter referring to the following:
*S - Slip renewable
*F - Fixed renewable
*L - Headless liner
*HL - Head liner
*P - Headless press-fit
*H - Head press-fit
The following two tables give the tolerances for the ID and OD.
Custom bushings
A common problem encountered is when two or more holes are too close for independent standard bushings. In this case one large renewable bushing can be made with two (or more) holes in the proper location (the first example in the image). Another possibility is to make a custom bushing with an eccentric
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-center, in geometry
* Eccentricity (graph theory) of a v ...
hole and then notches on the outside of the head are used to locate the proper position of the bushing for each location (the middle example in the image). Another common need for a custom bushing is when the hole needed is perpendicular jig plate; in this case a ''bracket bushing'' is used. It is a hardened piece of right angle steel that screw
A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to fa ...
s to the jig plate and is located with dowel pin
A dowel is a cylindrical rod, usually made of wood, plastic, or metal. In its original manufactured form, a dowel is called a ''dowel rod''. Dowel rods are often cut into short lengths called dowel pins. Dowels are commonly used as structural ...
s..
Design
In general, a drill bushing's length should be at least 2 times the nominal ID.References
Bibliography
* *{{Citation , last = Henriksen , first = Erik Karl , title = Jig and fixture design manual , publisher = Industrial Press Inc. , year = 1973 , url = https://books.google.com/books?id=OX9hspFzRAsC , isbn = 978-0-8311-1098-7 , postscript =. Metalworking tools