There are over 100,000 different types and sizes of ANSI and Economy standard bushings in this catalog, as well as many thousands of specialty bushings such as tungsten carbide, knurled, circuit board, oil groove, coolant chip-breaker and extra-thinwall. Selecting the exact bushing for your application could represent the proverbial "needle in a haystack" approach.

Fortunately, selection with this new, more comprehensive catalog is simplified by breaking down your requirements to basic considerations. For example,

• How will the bushing be used? (To drill, tap or ream?)

• What kind of bushing do you need? (For a steel jig or fixture, a plastic imbedment or potted fixture, a special circuit board drilling machine, etc.?

• What type of bushing do you need? (Will there be impact on the head? Do you want to replace the bushing in the fixture? If so, easily and quickly or only when the bushing wears out? Do you want to lubricate the drill in the bushing?)

• How long is the production run? (Will a standard 58 to 62 Rockwell C hardness do, or is the 78 to 80 hardness of a tungsten carbide bushing more desirable, even at a higher cost?)

• What size bushing do you need? (Hole size, length, O.D.? Does it have to fit your jig or are you going to machine it to fit?)

• Are there special requirements, such as a threaded O.D., a setscrew hole, special dimensions, or a mounting flange?

• If, after answering the other basic considerations, you determine that a special bushing is needed, ask yourself, "Can I change requirement (such as drill size) to those of a standard bushing?" You might save some money.

Answering these questions will help greatly in selecting the right bushing, for immediately certain considerations will be obvious. For instance, if you want to drill and ream, different bushings must be used because of the different O.D.'s of the drill and reamer. Several options are open: if you want to drill and ream using the same fixture hole you would want to use slip renewable bushings which can be changed quickly with little effort; if you are going to use successive holes in a fixture and you can leave the bushing in place, use either renewable or press fit bushings. Of course, if there will be impact on the head use a head-type bushing; if there will be no impact on the head and the bushing is to be pressed into the jig use a headless press fit bushing. Also, if cramped for space, check the head diameters of bushings; perhaps if one won't fit another will - keep in mind, however, that there are cost differences between the bushings; use the least expensive bushing for the existing space.

Here are some specifics:

BUSHINGS TYPES AND WHEN TO USE THEM.

HEADLESS PRESS FIT (or PLAIN) BUSHINGS. (ANSI designation P.) This is the most popular bushing, and the least expensive. It is generally used for single stage drilling operations.
It is an ideal bushing for low-cost jigs used on low-cost production where the bushing is pressed into a hole in the jig plate until flush with the surface of the jig plate. Because this bushing is headless, it permits close spacing where limited space, either in or for the jig, is a factor.

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This bushing is furnished either with a finish-ground outer diameter ready for insertion in the jig (Type P), or with an unground O.D. for customer grinding to his specified O.D. (Type PU).

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HEAD PRESS FIT BUSHINGS. (ANSI designation H.) This bushing is the same as the headless press fit, except that it has a head or shoulder on the top end. This type is used primarily where pressure might force the headless type through the jig. Either finish ground (Type H) or unground (Type HU) bushings are available.

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FIXED RENEWABLE BUSHINGS. ECONOMY TYPE R (ANSI designation XF) This bushing is used on long runs where the number of parts to be drilled is greater than the normal wear life of the bushing. This bushing is used with press fit bushing liners (see below). The bushing is held in place by a lock screw fitted into a milled recess in the head of the bushing. The bushing can be replaced when worn without removing the fixture from the production line.

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