Bridgeport Milling Machines

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First introduced in the 1940s, the various milling machines developed by Bridgeport Machine have become so successful and ubiquitous that "Bridgeport Milling Machine" has become a sort of generic catch-all term in the industry. They are all machines that are designed for shaping metal and other materials; unlike a drill press where the material is stationary on a platform, a milling machine moves the material back and forth, lathe-style, with cutting fluid sprayed to cool and lubricate the work (and wash away shavings).

The original Connecticut-based company (Bridgeport Machine) is now a part of Hardinge, a multinational family of companies that also includes brands like Kellenberger, Hauser, Tripet and Tschudin. The company has a presence in Switzerland, China, England, Germany and Taiwan.

Bridgeport milling machines include a few loose categories:

* Turret or vertical ram mills. These very common machines have a spindle where the work can be aligned in various ways for cuts, rather than being on a rigid spindle and moving the cutters.
* Knee or knee-and-column mills feature a table that ...
... can ride up and down the column on a vertically-adjustable "knee"
* C-frame mills are larger, industrial units. On a C-frame mill, the knee and spindle head are only mobile vertically. They feature a separate hydraulic motor for power feeds in various directions, a much larger table (to machine multiple pieces at once) and a 20- to 50-horsepower main motor.
* Jig borers are vertical mills designed to bore holes or do very light slot or face milling. These machines are designed for very tight tolerances and high levels of precision.
* Horizontal jig borers are large machines that can incorporate features from several kinds of machine tools. They are used for creating large industrial jigs or to machine and modify large parts that call for various features and a high level of precision.
* A bed mill is any machine where the spindle is on a pendant that moves up and down to manipulate the work in relation to the cutter.
* Floor mills are some of the largest and most complex cutting machines, with a row of rotary tables and the pendant spindle running on a set of tracks parallel to the tables. A carriage drops the spindle onto each table, then moves it on to the next table as the previous one is reset for the next operation. Most of these machines have been revamped from manual control to CNC digital systems.

Bridgeport-type machines can be controlled within a .001 inch (.025 mm) tolerance, by means of slides or lead screws. The revolution in machine control, however, started in the 1970s with the advent of CNC (computer numerical control) machines that used automation to produce a much more consistent and higher-quality product than a machinist could hope for using old-style manual controls. These days, CNC machines are available even at the hobbyist or light-industry level. As CNC software advances and the control systems become even more precise, the end result has been CNC Bridgeport-style machines that are much more affordable, compact and safer than previously thought possible.