Milling machine

How it works

A cutter with a number of teeth is turned by the spindle, and each tooth removes a small chip as it passes through the work. The workpiece is clamped to a table, usually in a vise or on the table itself, and the table feeds the work past the cutter. On the conventional knee-and-column machine the table can be moved from side to side, toward and away from the column, and up and down on a vertically adjustable knee, so that the cutter can reach any point of the work without resetting it.

The spindle is horizontal on a horizontal mill and vertical on a vertical mill. According to a New Jersey vocational curriculum, a vertical milling attachment mounted on the column of a horizontal machine lets it do face milling, end milling, drilling, boring and T-slot milling. Rudolph Bannow’s 1942 patent describes the general arrangement of a horizontal machine, in which a table feeds the work in three paths relative to an upright column and an overarm carries a self-powered machining unit, and claims an articulated support that lets the tool spindle be inclined and advanced to the work at any angle.

Anatomy

Column: The upright frame that carries the spindle head or overarm and guides the knee.
Knee: Slides on the column to raise and lower the table. The Science Museum Group describes the column-and-knee principle as providing vertical adjustment of the cutter relative to the work and credits it to Joseph R. Brown’s universal milling machine.
Saddle and table: Carry the work. Bannow’s patent describes a table mounted for feeding the work in three different paths relative to the upright column.
Spindle and arbor: The spindle turns the cutter, held on an arbor on a horizontal machine or in the spindle on a vertical machine.
Overarm and ram: On a horizontal machine, the overarm carries a unit above the table. Bannow’s patent covers a turret head mounted on top of the standard and an overarm that shifts longitudinally.
Dividing (index) head: Rotates the work by calculated fractions of a turn to space cuts around it; the New Jersey curriculum lists dividing head and footstock among the equipment of the horizontal milling machine.

Variants

Plain horizontal mill: Roe reports that plain milling machines had been in use for many years by the American Civil War, and that Brown & Sharpe sold a plain miller designed by Frederick W. Howe for years.
Universal milling machine: The Brown & Sharpe design of 1861–62, developed to cut spiral flutes in twist drills and for general machine-shop work.
Vertical mill: A machine with its spindle vertical; the curriculum describes a head that can be swiveled for angular surfaces.
Ram-type turret mill (Bridgeport): The vertical machine with a swiveling head on a sliding ram that the Bridgeport firm first shipped in 1938; the American Precision Museum says that more than a quarter of a million have been built.
CNC mill: Covered in a separate entry.

Specifications

Spindle speed steps (original Bridgeport head) · steps: The American Precision Museum says the Bridgeport mills have five belt steps, while the earlier high-speed attachment head had four and a quarter horsepower motor.
Table travel · in or mm: No sourced typical value.
Spindle taper · taper designation: No sourced designation.

Made to

ANSI B11.8
EN 13128
ISO 16090-1
ISO 230-1

Safety and care

Safety

The Canadian Centre for Occupational Health and Safety (CCOHS) advises against wearing gloves, rings, watches or loose clothing, and tying back and confining long hair.
CCOHS advises that work not be mounted, measured or adjusted until the cutter has completely stopped, and that no adjustment be made while the machine is running.
CCOHS advises keeping hands at least 30 cm (12 in.) from a revolving cutter and not reaching over or near it.
CCOHS advises against an excessively heavy cut or feed, which can break the cutter and send flying pieces.
CCOHS advises not leaning or resting the hands on a moving table, and not using paper shims to check the distance from cutter to stock.
CCOHS advises not moving operating levers without knowing what they control.

Tips

Choose climb or conventional milling for the job
A New York State instructor’s guide lists the advantages of climb milling as better finish, less tendency to chatter and lower power requirements, and the advantages of conventional milling as elimination of backlash and cutter life that is not affected by sandy or scaly surfaces. The same guide’s job sheet for the vise-held workpiece says not to climb mill.1
Put the cutting force against the solid jaw and keep the work deep in the vise
The New York guide’s job sheet directs that the cutter be mounted so the cutting forces are against the solid jaw of the vise, and that the workpiece be kept as deep in the vise as possible.1
Tilt the head instead of re-clamping the work
Bannow’s patent states that, on earlier machines, many desired operations were impossible or required changing the setup of the work on the table, which slows production and risks inaccuracy. His articulated head support is meant to let the tool spindle approach the work at any inclination without moving the work.1
Use a two-lipped end mill where the cutter must start in the work
The New Jersey curriculum describes the two-lipped end mill, also called a slotting mill, as having only two teeth on the circumference with the end teeth cut to center. It lists the T-slot cutter as made with staggered teeth and side cutting faces and used after a straight slot has first been cut with a side mill.1
Convert a horizontal mill with a vertical attachment
The New Jersey curriculum describes a vertical milling attachment mounted on the face of the column that lets a plain or universal horizontal mill do face milling, end milling, drilling, boring and T-slot milling.1

History

Earliest documented

before 1782 (earliest surviving milling cutter); 1772 (earliest published illustration of a light milling machine, per Roe)

France (cutter by Jacques de Vaucanson; the Encyclopédie of 1772)

Roe reports that the oldest milling cutter known, which he says was used for cutting gear teeth, was made some time before 1782 by the French mechanic Jacques de Vaucanson, with fine teeth that appear to have been cut with chisels, and that it came into the possession of the Brown & Sharpe Manufacturing Company about 1895. He also notes that a light sort of milling machine is shown in the French Encyclopédie of 1772. Roe states that the first successful milling machine was built by Eli Whitney before 1818; later historians dispute this (see disputed).1

Milling grew out of the need to produce identical parts in quantity. The Yale–New Haven Teachers Institute unit states that interchangeability requires precision machine tools and associates the milling machine with the firearms contractors of Connecticut and Massachusetts. Roe supports the connection from the other direction: in 1855 the 157 machines for gun manufacture sent from the United States to England included seventy-four millers and twenty-three drilling machines, with scarcely a lathe in the list. Both Roe and the Science Museum Group present the universal milling machine as the replacement for laborious hand filing of twist-drill grooves.

Who built the first milling machine is disputed. Older reference works, quoted by American Heritage, said that Whitney’s plain milling machine, built before 1818, was believed to be the first successful machine of its kind, and Roe repeats the claim. Edward Battison’s 1966 article in the Smithsonian Journal of History, as summarized by American Heritage, concluded that there is no evidence Whitney developed or used a true milling machine and that the machine at Whitneyville was probably made after his death in 1825. The Yale unit and the Eli Whitney Museum credit Simeon North with one of the first American milling machines, and the Yale unit quotes Merritt Roe Smith’s view that the machine did not spring from one mind but took form through cooperation, transfer and convergence among armory mechanics.

The universal milling machine can be dated more firmly. Roe records that Joseph R. Brown built the first machine for the Providence Tool Company, which bought it on 14 March 1862, to mill the flutes in twist drills, after Howe, then superintendent there, had watched a workman filing spiral grooves with a rat-tail file and judged the method too expensive. The Science Museum Group describes the machine as capable not only of cutting spirals in twist drills but of general work in machine shops, and says it introduced the column and knee principle for vertical adjustment of the cutter. Roe adds that Howe himself never claimed to have invented it.

In the twentieth century the machine most often called a milling machine in small shops is the ram-and-turret vertical mill that Rudolph Bannow brought out in 1938. The American Precision Museum describes it as developed from a milling head the firm had sold as an attachment since 1932, and says the machine became the foundation of the tool and die business of thousands of small job shops. Bannow’s patent, filed in 1939, addresses the limits of conventional machines in setting the tool to angles and positions without moving the work. The Science Museum Group holds a Bridgeport machine (object 1975-14) credited to Bridgeport Machines Ltd. and Adcock-Shipley.

Timeline

1772
A light milling machine appears in the French Encyclopédie, according to Roe.1
before 1782
Jacques de Vaucanson makes the oldest known milling cutter, for gear teeth, now held by Brown & Sharpe per Roe.1
by 1820
Both Eli Whitney and Simeon North were using plain milling by 1820, according to Roe.1
c.1827
Woodbury and Battison, as summarized by the American Precision Museum, date the Whitneyville milling machine to about 1827, after Whitney’s death in 1825.1 2
1852
Frederick W. Howe is reported by Fitch (Census of 1880) to have designed a universal miller; Roe says Howe’s drawings show a machine of different design from the later Brown & Sharpe universal miller.1
1855
A shipment of 157 machines for gun manufacture is sent from the United States to England, including seventy-four millers and twenty-three drilling machines, per Roe.1
1861
The Providence Tool Company receives a musket contract that requires many drilling operations; Frederick W. Howe asks Joseph R. Brown of Brown & Sharpe for a way to machine twist-drill grooves.1 2
1862
The first Brown & Sharpe universal milling machine is built and sold to the Providence Tool Company on 14 March 1862; the first published account appears in Scientific American on 27 December 1862, and ten machines are sold in the year.1
1889
The Cincinnati Milling Machine Company is formed, from the Cincinnati Screw & Tap Company, which began about 1880 when Frederick Holtz built a milling machine with a wooden base for fluting taps.1
1927
Rudolph Bannow buys the Bridgeport Pattern & Model Works; Magnus Wahlstrom joins as a partner in 1929.1 2
1932
The firm begins selling a high-speed milling head as an attachment for heavier machines.1
1936
Bannow conceives a machine built around the milling head; the American Precision Museum repeats the account that he sketched it on a paper bag.1 2
1938
The first Bridgeport turret milling machine is shipped; its serial number 1 carries the strip S38-001.1
1939
Bannow files the application for US Patent 2,275,291, granted 3 March 1942.1

Where the sources disagree

Who built the first milling machine?

Eli Whitney, before 1818. The Dictionary of American Biography, as quoted by American Heritage, calls the surviving plain milling machine the first successful machine of its kind; Roe says the first successful one was built by Whitney before 1818 and is held at the Sheffield Scientific School of Yale.1 2
Dictionary of American Biography (via American Heritage); Roe
No true milling machine was developed or used by Whitney, and the machine named for him was probably made after his death in 1825. Battison suggests that Robert Johnson of Middletown, Connecticut made the first true milling machine.1
Edward A. Battison, 1966 (as summarized by American Heritage)
Simeon North originated it. Battison’s later article “A New Look at the ‘Whitney’ Milling Machine” is described as arguing that the milling machine originated with North, and the Whitney machine is dated to the modernization of the Whitneyville factory in 1827.1 2
Edwin Battison (as summarized by the Yale–New Haven Teachers Institute); Woodbury and Battison (as summarized by the American Precision Museum)
No single inventor. The machine took form through a process of cooperation, transfer and convergence.1
Merritt Roe Smith (as quoted in the Yale–New Haven Teachers Institute unit)

Who designed the first universal milling machine, and when?

Frederick W. Howe in 1852, according to Fitch’s report in the Census of 1880.1
Fitch, as reported by Roe
Joseph R. Brown, 1861–62, at Howe’s suggestion; Roe adds that Howe’s earlier machine was of radically different design.1
Roe
In a footnote Roe gives 1871 for Brown’s invention, which conflicts with his own 1861–62 in the text. The Science Museum Group dates its example of the Brown and Sharpe first universal machine 1865 while describing the 1861 contract that prompted it.1 2
Roe; Science Museum Group

Gaps in the record (8)

Battison’s 1966 and 1973 articles and Smith’s article on Hall, North and the milling machine were not accessible and are known only through summaries.
Woodbury’s Studies in the History of Machine Tools was not available in full text; the date c.1827 for the Whitney machine is from a museum summary.
No patent has been located for Brown’s universal milling machine or Howe’s machines.
The Lincoln miller and the origin of the knee-and-column layout before Brown are not documented beyond Roe’s brief mentions.
No sourced typical specifications (table travel, spindle taper, power) are given.
Care and maintenance have not been sourced; care is empty.
Origin of numerical control for milling is left to the CNC mill entry.
The Smithsonian National Museum of American History object texts for the Whitney milling machine could not be reached from this machine.