A “Milling Machine” is a machine tool that rotates a circular tool with numerous cutting edges arranged symmetrically about its axis, called a milling cutter. The metal work piece is usually held in a vise clamped to a table that can move in three perpendicular directions. Cutters of many shapes and sizes are available for a wide variety of milling operations. Milling machines cut flat surfaces, grooves, shoulders, inclined surfaces, dovetails, and T-slots. Various form-tooth cutters are used for cutting concave forms and convex grooves, for rounding corners, and for cutting gear teeth. These machines are also called Millers.
Milling machines evolved from the practice of rotary filing—that is, running a circular cutter with file-like teeth in the headstock of a lathe. Rotary filing and, later, true milling were developed to reduce time and effort spent hand-filing.
Although some historians credit the first true milling machine to the inventor Eli Whitney, other historians and new historical discoveries point to a variety of inventors and machine builders to include: Robert Johnson of Middletown, Connecticut; Captain John H. Hall of the Harpers Ferry armory; Simeon North of the Staddle Hill factory in Middletown; Roswell Lee of the Springfield armory; and Thomas Blanchard.
We may never know who actually built the first Miller as most of the milling machines development was done in private shops over a period of time and due to proprietary design secrets as it developed little historical data was kept for posterity. As one man developed a concept others continually built upon them.
What we do know however is the process of development and how milling machines were improved over a short period of time to become one of the leading machines used in the machining industry today. I have bulleted a few milestones that I thought were interesting:
- Rotary filing long predated milling. A rotary file by Jacques de Vaucanson, circa 1760, is well known.
- James Nasmyth built a milling machine very advanced for its time between 1829 and 1831. It was tooled to mill the six sides of a hex nut that was mounted in a six-way indexing fixture.
- During the 1840-60’s some of the key men in milling machine development included Frederick W. Howe, Francis A. Pratt, Elisha K. Root, and others. (These same men during the same era were also busy developing the state of the art in turret lathes.
- 1870’s to World War I In these decades, Brown & Sharpe and the Cincinnati Milling Machine Company dominated the milling machine field.
- World War I and Interwar period: Around the end of World War I, machine tool control advanced in various ways that laid the groundwork for later CNC technology. The jig borer popularized the ideas of coordinate dimensioning (dimensioning of all locations on the part from a single reference point); working routinely in “tenths” (ten-thousandths of an inch, 0.0001″) as an everyday machine capability; and using the control to go straight from drawing to part, circumventing jig-making.
- In 1936, Rudolph Bannow (1897–1962) conceived of a major improvement to the milling machine. His company commenced manufacturing a new knee-and-column vertical mill in 1938. This was the Bridgeport milling machine, often called a ram-type or turret-type mill because its head has sliding-ram and rotating-turret mounting.