Bridgeport (machine tool brand)

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The Bridgeport logo as cast into the head of a Bridgeport Knee Mill.
A full view of a Sharp Machinery 3 axis vertical mill. An example of a Bridgeport clone. The head is mounted on the ram by joints that allow it to swivel in two directions. The ram can slide back and forth on the turret, which can swivel on the column. The table sits on the knee, and it can move horizontally in the X and Y axes. The knee rides up and down the column (one form of Z-axis movement), and the head contains a quill in which the spindle can slide up and down (another form of Z-axis movement or, when the head is swiveled, an additional axis).
A Bridgeport variant that has been retrofitted with motors and controls to function as a CNC machine. Sharp Machinery brand mill and Anilam brand CNC controllers.

Bridgeport is a brand of milling machines and machining centers, which are machine tools used in the machining industries. The brand was produced by Bridgeport Machines, Inc. from 1938 until 2004, when it was acquired by Hardinge, Inc., its current owner. Hardinge is a multinational corporation whose machine tool brands include Hardinge, Bridgeport, Kellenberger, Hauser, Tripet, and Tschudin. It currently has subsidiaries in England, Germany, Switzerland, China, and Taiwan, ROC.

History[edit]

The original corporation was founded in Bridgeport, Connecticut and started selling its machines in 1938. It became famous in the following decades for these small- and medium-sized vertical milling machines, with their iconic form of a quill-equipped multiple-speed vertical milling head with a ram-on-turret mounting over a knee-and-column base. The American Precision Museum's biography of Rudolph Bannow[1] reports that he conceived the iconic design in 1936 as the logical machine on which to mount the milling head already being built by the Bridgeport Pattern and Model Works (which he owned with partner Magnus Wahlstrom). The first Bridgeport milling machine (serial number 1) is on display at the Museum.[2]

Bridgeport's manual milling machines have been so successful and ubiquitous that, within the machining industries and among hobbyists, the Bridgeport is an archetypical example of that class of machine, and the term "Bridgeport" is often used to refer to any vertical milling machine of the same configuration, regardless of make. Many other companies have cloned the form. Today the Bridgeport brand still produces this configuration in both manual and CNC versions, although tool-changer-equipped machining centers are now equally prominent members of the product line.

Bridgeport manual milling machines have come in many types and sizes over the years, including (but not limited to) the C head (original), R head (heavy duty C head), M head, J head (and high speed, 5440 RPM version), 2J1 1/2 head (1.5 HP Vari-Speed), 2J2 (2HP Vari-speed), and Series II head (4HP Vari-speed). All of the heads offer variable speeds, the earlier ones via a step pulley (cone pulley) and the later ones via electrically or electronically modulated variable-speed drive. Typical table sizes are 9″ × 49″ (Y and X, respectively) and 10″ × 54″. Machine tapers for toolholding include Morse tapers (on early models) and the R8 taper (a widely used standard that Bridgeport created) on most models. Both Morse and R8 allow for both collets and solid holders; and a drill chuck can be held by either of the latter. Machine slides are of the dovetail type, and rotary bearings are mostly of the roller and ball types.

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