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Bridgeport Mill

4 minute read

Bridgeport Mill

A Legacy of Precision and Versatility

The Bridgeport Mill, specifically the Series I, is a cornerstone in the world of machining, renowned for its precision, versatility, and durability. This milling machine has been a staple in workshops and manufacturing facilities for decades, earning a reputation as a reliable and essential tool for machinists and engineers alike.

Historical Significance

The Bridgeport Mill was first introduced in 1938 by Bridgeport Machines, Inc., and it quickly became the standard for milling machines. Its innovative design and robust construction set it apart from other milling machines of the time. The Series I model, in particular, has become synonymous with the term “milling machine,” often referred to simply as a “Bridgeport.”

Key Features and Capabilities

The Bridgeport Series I Mill is designed to handle a wide range of milling operations with precision and ease. It features a knee-type design, which allows for vertical movement of the workpiece, providing greater flexibility and control. The machine’s table can move longitudinally (X-axis) and crosswise (Y-axis), while the quill allows for vertical (Z-axis) movement, making it suitable for various complex machining tasks.

Table and Travel:

  • Table Size: 49 inches x 9 inches (1245 mm x 229 mm)
  • X-Axis Travel: 31 inches (787 mm) without power feed, 33.5 inches (851 mm) with power feed
  • Y-Axis Travel: 12 inches (305 mm)
  • Z-Axis Travel: 16 inches (406 mm) without flood coolant, 15 inches (381 mm) with flood coolant
  • Ram Travel: 12 inches (305 mm)

Spindle and Quill:

  • Spindle Taper: R-8 (standard), with optional #30 ISO for Erickson Quick-Change tooling
  • Spindle Speed Range: 60 to 4200 RPM, adjustable via a variable speed dial
  • Quill Travel: 5 inches (127 mm)
  • Power Feed Rates: 0.0015, 0.003, and 0.006 inches per revolution

Advanced Control and Safety Features

The Bridgeport Mill is equipped with a range of controls and safety features to ensure precise operation and operator safety. The high-low range switch allows for easy adjustment between high-speed and low-speed operations, while the variable speed dial provides visible indication of the operating speed range. The spindle brake can be moved in either direction to stop the spindle, and the quill feed selector offers three feed rates for different machining needs.

Safety is a paramount concern, and the Bridgeport Mill includes several features to protect operators. These include a spindle brake, quill stop knob, and micrometer nut for setting precise depths. The machine also comes with a general-purpose point of operation shield to protect against flying chips and splashing coolant. Additionally, the machine’s design adheres to ANSI and OSHA standards for manual milling, drilling, and boring machines.

Maintenance and Durability

The Bridgeport Mill is known for its durability and ease of maintenance. Regular lubrication is essential to keep the machine running smoothly, and the Series I model includes a detailed lubrication system to ensure all moving parts are properly maintained. The machine’s robust construction, including a solid cast iron frame and precision-ground ways, ensures long-term reliability and accuracy.

Applications and Benefits

The versatility of the Bridgeport Mill makes it suitable for a wide range of applications, from prototyping and custom fabrication to small-scale production runs. Its ability to handle various materials, including metals, plastics, and composites, makes it an invaluable tool in industries such as aerospace, automotive, and general engineering.

The Bridgeport Mill’s precision and flexibility allow for the creation of complex parts with tight tolerances, making it ideal for tasks such as milling, drilling, boring, and tapping. Its user-friendly controls and safety features make it accessible to both experienced machinists and those new to milling operations.


The Bridgeport Series I Mill remains a benchmark in the world of machining, offering unmatched precision, versatility, and durability. Its advanced features, robust construction, and comprehensive safety measures make it an essential tool for any workshop or manufacturing facility. Whether you are a seasoned machinist or a newcomer to the field, the Bridgeport Mill provides the reliability and performance needed to tackle a wide range of machining tasks.

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