USA 09The Lineage of American Gear Machines

Indexing and form gear cutting (1833–1883)

In the first half of the 19th century, metal gears were either used as cast or finished by hand. To cut teeth correctly by machine, you first need the technique of dividing a circle accurately into equal parts (indexing). In America, the people who had it were makers of clocks and surveying instruments. David Brown and his son Joseph R. Brown, who opened a clock and instrument shop in Providence, Rhode Island, in 1833, were already taking orders for spur, helical and bevel gears and index plates in a newspaper advertisement that same year^[1][2]. In 1853 Lucian Sharpe joined, and the shop became J. R. Brown & Sharpe (later Brown & Sharpe)^[1].

In 1855 Brown built a precision gear cutter for the company's own use. Its divisions were copied from a British-made dividing engine at the US Coast Survey, and it could cut gears up to about 37 inches (about 940 mm) in diameter. It was not for sale; it was used with great care in a room of its own to make index plates and precision gears^[2][1]. The indexing accuracy of instrument making was thus the starting point for the accuracy of gear cutting machines.

Formed cutters that keep their shape when resharpened (1864)

Cutting teeth by the form method requires a cutter with the same shape as the tooth space (a form milling cutter). But the teeth of milling cutters at the time were filed by hand, and their shape was lost every time they were resharpened. Brown devised a cutter that solved this and received US Patent 45,294 on November 29, 1864^[3]. The back of each tooth is relieved (backed off), so that if only the rake face is resharpened, the cutting profile stays the same however many times it is ground. Roe describes it as a formed milling cutter, devised for cutting gear teeth, whose profile stays correct after resharpening^[1].

This cutter even changed how tooth forms were chosen. According to Woodbury, Brown & Sharpe listed sets of gear cutters in its first catalog in 1867. With the cycloidal tooth form then dominant, cutting everything from a 12-tooth pinion to a rack required a set of 24 cutters per pitch, but with the involute form 8 were enough. Since the company was the only maker of commercial gear cutters, its reputation is said to have greatly helped the spread of the involute tooth form^[2]. The company's Practical Treatise on Gearing of 1886 shows that eight cutters per pitch (No.1–No.8) can cut every tooth count from 12 up for involute gears^[8]. The idea of the "8-cutter set for standard gears" still used on Japanese shop floors today comes from here.

Automatic gear cutting machines (1877)

After the Civil War, demand for gears for sewing machines and farm machinery grew, and skilled workers ran short. What was needed was an automatic gear cutter that, once a blank was mounted, would cut every tooth by itself and stop. Around 1860 Gage, Warner & Whitney of Nashua, New Hampshire, built an automatic machine that reversed the feed using the force of a falling weight and indexed on the return stroke. In 1867 William Sellers of Philadelphia exhibited at the Paris Exposition an automatic gear cutter in which no motion could begin until the previous one was complete^[2].

They were first sold as production machines in 1877. That year Brown & Sharpe and Gould & Eberhardt of Newark, New Jersey, in the United States, and Craven Brothers in Britain, brought out automatic gear cutters^[2]. Brown & Sharpe's two models were designed by Edward H. Parks; the small one was used for small spur and bevel gears for sewing machines, and the large one for gears for general machinery^[1]. According to company records, 16 of the small model were built in 1879, priced at $650^[2]. Indexing was by worm and worm wheel, with the tooth count set by change ratchet wheels; the big change on the shop floor was that one worker could now tend several machines. Woodbury places such automatic gear cutters, alongside automatic screw machines, as "pioneers of automation"^[2].

Large bevel gears by template (Gleason, Corliss)

On a bevel gear the teeth get smaller from the outside inward, so a cutter of a single shape cannot cut a correct tooth form. The method used instead was to run a roller along an enlarged template of the tooth form and move a planing tool accordingly. William Gleason, who worked at Colt's armory and then started a shop in Rochester, New York, in 1865, built his first bevel gear planer in 1874. The company's history calls this "the beginning of a new industry: bevel gears"^[4][1]. At the 1876 Centennial Exhibition in Philadelphia, George H. Corliss built and showed a template-type gear cutter to cut the large bevel gears of the great steam engine that powered the exhibition, and it attracted attention^[2].

Woodbury names Gleason as a leading maker of template-type gear cutters. Flanders's 1909 book reports that Gleason's template-type spur gear planer could cut gears up to 20 feet (about 6 m) in diameter^[2][6]. Roe wrote in 1916 that Gleason had started out with general-purpose machine tools and narrowed its line to bevel gear cutting machines alone, becoming a specialist company^[1]. The Smithsonian's National Museum of American History lists a Gleason bevel gear planer in its collection^[48].

What it means on the shop floor. The number of a formed cutter (No.1–No.8) indicates the range of tooth counts it can cut. Cutting a tooth count at the end of a range makes the tooth form slightly off, so today the rule is to cut gears that need accuracy by a generating method (hob, pinion cutter). Even so, for small lots of repair parts and work on a dividing head, the 8-cutter set dating back to Brown & Sharpe is still useful.

The birth of generating gear cutting and the hobbing machine (1884–1912)

Both the form method and the template method needed "someone to make the correct tooth form first." What made this unnecessary was the generating method. Treat the cutter as one tooth of a basic rack (a gear with straight teeth) and move the gear blank as if rolling it along that rack, and a correct involute profile is cut naturally, even if the cutter's edge is a simple straight line.

Bilgram's bevel gear generator (1884)

The man who built a practically useful machine on this idea was Hugo Bilgram of Philadelphia. He applied in 1882 and on March 11, 1884, received US Patent 294,844 for a "bevel-gear cutter"^[5]. The planing tool only reciprocates, while the blank is "rolled" by two steel bands, swinging about the apex of the pitch cone. Woodbury calls it the first machine of the "molding-generating" type, in which a cutter with a rack tooth form generates the gear as if in mesh with it, and writes that the demand behind it came from the fashion for chainless bicycles^[2]. Flanders's 1909 book also describes Bilgram's machine in detail^[6]. The bevel gear tooth form produced by Bilgram's machine was a new shape, neither involute nor cycloidal, which George B. Grant of Boston named the "octoid"^[2]. In 1901–02 Bilgram also brought out automatic generators for spur and bevel gears, which cut a little into every tooth and finished the tooth form over many revolutions^[2].

George B. Grant: gear books and the first hobbing machine

Grant did major work in both theory and practice. In his Handbook of the Teeth of Gears (1885) and Odontics (1891) he showed mathematically that the involute tooth form is superior to the cycloidal in efficiency, strength and tolerance of center-distance errors. In 1885, he says, cycloidal teeth were still the more common in factories^[2]. On the machine side, US Patent 405,030, applied for in 1887 and granted on June 11, 1889, showed a machine that rotates a hob (a worm with cutting edges) together with the blank while feeding the hob across the face width to cut spur gears and worm wheels^[9]. Woodbury regards this as the first hobbing machine that was certainly put to actual use^[2]. Grant also patented a bevel gear planer that traced the tooth form with the tool point (1889) and a bevel gear generator for the "planoid" tooth form (1894)^[10][11].

Around the same time, Pratt & Whitney built the "epicycloidal engine" designed by Ambrose Swasey. It was a machine not for gears but for cutting the templates of gear cutters to the correct tooth form^[2]. In 1885 Swasey also patented a machine that generated spur gears with a milling cutter shaped like a rack tooth, but it was complex and did not spread^[7][2].

The Fellows gear shaper (1896)

The most successful spur gear generator came from Edwin R. Fellows of Springfield, Vermont: the gear shaping machine (gear shaper). Fellows had no formal training in engineering; he joined Jones & Lamson and became chief draftsman. According to Roe, Fellows, a 22-year-old window dresser at a clothing store in Torrington, Connecticut, came along when James Hartness moved to Springfield, spent a week cutting slots in screw heads, and then moved to the drafting room^[1]. The American Precision Museum explains that Hartness, who wanted Jones & Lamson to concentrate on the flat turret lathe, encouraged Fellows to go independent, and in July 1896 Fellows founded a company with capital from Hartness and other local businessmen. The first 36-inch prototype was built in Fitchburg the same year and was not sold^[12].

The key to the mechanism is the cutter. The cutter is a pinion cutter shaped like a gear itself; the cutter and blank are meshed like a pair of gears and turned slowly while the cutter reciprocates up and down to cut. Patents for the machine (US Patent 579,708) and the cutter (579,570) were granted on March 30, 1897^[14][15]. The cutter is ground after hardening to finish its tooth form. Woodbury says the heart of Fellows's work was the cutter grinder, which grinds the hardened cutter by rolling it against the flat face of a wheel (standing in for one flank of a rack tooth), and that this was made possible by progress in grinding machines around 1890^[2]. American Machinist of December 9, 1897, featured "The Fellows Gear Shaper" starting from its cover, reporting it as a new method that needed neither templates nor hand finishing^[16]. In 1899 the Franklin Institute awarded Fellows the John Scott Medal^[2].

The strength of the gear shaper is that it can cut where a hob has no room to run out, such as internal gears and gears at the root of a stepped shaft. Flanders's 1909 book shows, with photographs, Fellows machines cutting internal gears and an attachment for cutting racks^[6]. Helical gears are cut by twisting the cutter spindle along a helical guide as it moves up and down. Flanders writes that this method was part of Fellows's original concept, and later, in 1939, Fellows's company applied for a patent on a helical guide that could switch between right-hand and left-hand helices^[6][35].

Gleason's bevel gear generator (1898)

At Gleason, William's son James E. Gleason joined the company in 1892 and took charge of machine design^[4]. US Patent 605,249 of June 7, 1898, covered a bevel gear generator that finished both sides of the tooth space with rotating cutters and was fully automatic from the start^[17]. According to Woodbury, whereas Bilgram's machine held the basic rack fixed and rolled the blank, Gleason's machine turned the blank in a fixed position and moved the basic gear (rack) instead. The relative motion is the same^[2]. In 1900 Oscar J. Beale of Brown & Sharpe also designed a bevel gear generator that cut both sides of the tooth space at once with two toothed disks, and Woodbury rates it as the most commercially important generator after Fellows's^[2]. Gleason was incorporated as The Gleason Works in 1903 and exhibited a 15-inch straight bevel gear generator at the Liège International Exposition in 1905^[4].

Hobbing machines: Pfauter's patent and American makers

Unlike methods that cut by reciprocating one tooth at a time, hobbing cuts continuously, so it is far more productive. But according to Woodbury, during the 19th century it was slow to spread: it was hard to grind hobs to the correct form after hardening, aligning the axes of hob and blank accurately took effort, and there was a suspicion that "hobbing leaves small flats on the tooth flanks"^[2]. The breakthrough came from Robert Hermann Pfauter of Chemnitz, Germany. He took a German patent in 1897, and US Patent 640,728 was granted on January 2, 1900^[19][18]. Woodbury says the basis of the hobbing machine was established when Pfauter combined tilting the hob axis by the helix angle while feeding it with synchronizing blank and hob through a gear train, and used a differential to cut helical gears as well^[2] (for details, see the chapter on German gear machines).

American makers soon followed. Brown & Sharpe records show that in 1904 its engineers visited the works of De Laval (steam turbines), Newton and Bilgram to study hobbing, and reported that hobs must be ground after hardening, that axis alignment was difficult, and that the machines had to be built heavy^[2]. Flanders's 1909 book includes photographs of a horizontal hobbing machine by Gould & Eberhardt and of a Grant-Lees Machine Co. hobbing machine cutting helical gears and worm wheels^[6]. In June of the same year, 1909, E. J. Lees, vice president of Grant-Lees, founded the Lees-Bradner Company in Cleveland with H. T. Bradner and put a gear generator of his own design on the market^[22][23]. According to Woodbury, the book covered 24 makers of hobbing machines, all of which had been built since 1900 to meet the demand from automobiles and other industries^[2]. After continued research, Brown & Sharpe brought out the No.34 and No.44 hobbing machines in 1915^[2]. Barber-Colman of Rockford, Illinois, which according to Roe began making tools and gear cutters around 1896^[1], brought out the No. 12 hobbing machine for production work in 1910^[24][25], later became America's leading hobbing machine maker, and its designs are carried on today by Bourn & Koch^[45].

The beginnings of gear grinding, and the debate over standards

Hardening distorts gears. So the idea arose of finishing hardened teeth with a grinding wheel: gear grinding. Around 1899 Leland & Faulconer of Detroit built a machine that ground hardened teeth along a template, for the light bevel gears of chainless bicycles^[2]. In grinding, the wheel itself wears away, so keeping the tooth form requires a mechanism to true the wheel's shape and compensate for the wear. Ward and Taylor of the Gear Grinding Machine Co. of Detroit patented, on May 26, 1908, a mechanism that formed the wheel automatically with a diamond and had the machine compensate for its wear, and Woodbury regards this as the decisive invention that made gear grinding practical^[21][2] (for the history of grinding machines themselves, see Chapter 8: Grinding Machines).

Work on standards for gear interchangeability also began in this period. When Flanders presented a system of interchangeable involute gearing to ASME (the American Society of Mechanical Engineers) in December 1908, ASME formed a committee in January 1909 and held joint discussions with the British institution in 1910. 1910 was also the year of the "hobbing controversy" over whether hobbed tooth flanks have flats, which was settled by Flanders's experiments^[2].

The automobile and the two world wars (1913–1945)

In the 20th century the automobile became the biggest user of gears. The bevel gears that turn the engine's rotation through a right angle in the rear axle, and the helical gears of the transmission, had to be made strong, quiet, cheap and in great quantity. Woodbury writes that the quantity and quality of gears the automobile demanded were without precedent^[2].

Spiral bevel gears (1913)

Straight bevel gear teeth engage and leave one at a time, so they are noisy at high speed. If the teeth are curved, several teeth are always engaged, slightly offset from one another, and power is transmitted smoothly. According to Gleason's company history, it was in 1913 that James E. Gleason and Arthur Stewart designed the spiral bevel gear at Gleason^[4]. On May 26, 1913, James E. Gleason applied for a patent on a machine to generate curved teeth automatically (granted 1919)^[26]. The next year, 1914, the first production 15-inch automatic spiral bevel gear generator went on sale^[4].

Hypoid gears (1924)

Ernest Wildhaber, who came from Switzerland in 1919, was in charge of gear theory at Gleason and obtained 279 patents during his lifetime^[27]. According to Gleason's technical material, Wildhaber invented the hypoid gear in 1924^[27]. It is a bevel gear with the pinion axis offset from the center of the gear; because it lets the propeller shaft sit lower, the car body can be lowered by 50 mm or more. The patents "Gearing," applied for on March 25, 1924 (granted 1928), and "Hypoid Gear," applied for in 1927 and granted in 1931, were assigned in Wildhaber's name to Gleason^[29][30]. Gleason's company history names the 1927 Packard 426 as the first production car with a hypoid differential, and its technical material says that within five years of the invention all the major automakers had switched to hypoid rear axles^[4][27] (both are the company's own accounts).

AGMA and the technology of measuring gears

In 1916 AGMA (the American Gear Manufacturers Association) was formed, with Gleason as a founding member^[4]. Woodbury cites a record of a Brown & Sharpe engineer lecturing on gear inspection at an AGMA meeting in September 1917^[2]. Gear measurement at the time used special micrometers for pitch-circle dimensions or measurement over pins (wires), which revealed only part of the tooth form. Woodbury says gears could finally be inspected properly thanks to the optical method of inspecting screw threads (the screw thread comparator), which James Hartness of Springfield applied for in 1919 and was granted in 1921, and to the application of its principle to gears^[28][2]. Fellows's company also applied in 1933 for a patent on a machine that measured tooth profile and helix (lead)^[34]. Tooth form standards were developed into today's basis by AGMA committees under the guidance of Earle Buckingham (MIT)^[2].

Shaving and gear grinding

After World War I, high accuracy came to be demanded even of unhardened gears, giving rise to the gear shaving machine, which pares thin layers off tooth flanks rough-cut quickly with a hob or shaper, to true them. Woodbury cites as a representative example a Pratt & Whitney machine presented at ASME in 1928^[2]. It was National Broach & Machine of Detroit that made shaving a production process. When a gear-shaped cutter (shaving cutter) is meshed with the blank on crossed axes and rotated, sliding along the tooth flank produces thin chips. The company's Robert S. Drummond applied in 1931 for a patent on a gear finishing method (granted 1935), and in the late 1930s a series of shaving patents, including "Surface Shaving," were filed in the name of National Broach & Machine^[31][32]. Shaving removed the feed marks of hobbing from the tooth flanks and also made small modifications of tooth profile and lead (crowning) possible.

For finishing after hardening, Gleason began developing grinders for spiral bevel and hypoid gears in 1931 and put them on sale in 1938. By the end of the 1930s, Gleason's Zerol bevel gears were widely used in aircraft, which needed hardened high-precision gears^[4]. Fellows also applied for a patent on a helical gear grinder in 1931, expanding from gear cutting into finishing and measurement^[33].

The two world wars

In World War I, Gleason cut thousands of gears for aircraft, trucks, tractors and artillery^[4]. In the 1930s it also helped set up the gear department of the Stalingrad Tractor Plant in the Soviet Union^[4]. In World War II, Gleason entered war production from 1940 and, with more than 2,500 employees, made gears not only for vehicle transmissions and differentials but also for radar, searchlights and fire-control equipment. It received the wartime production "E" award five times, and the company says all the gears and pinions of the M4 Sherman tank were cut on Gleason machines^[4]. In 1942 it launched the Curvic coupling devised by Wildhaber (a coupling with curved teeth on its face), which was used in jet engines^[4].

Postwar mass production and finishing (1945–1987)

Postwar American gear making centered on automobile mass-production lines. Woodbury wrote in 1958 that many gears were now rough-cut with a hob, hardened, and finished by gear grinding, extending to gears the idea of "production grinding" that Norton had begun with cylindrical grinding. Unhardened gears were finished by shaving, and those needing even higher accuracy and finer surfaces by meshing them with a gear-shaped hone made of resin mixed with abrasive, devised by National Broach & Machine, to polish them: gear honing^[2].

Gleason's production machines

Gleason set up a research and development department in 1945^[4], and by 1954 the Rochester plant covered 27 acres with more than 600,000 square feet (about 56,000 m²) of floor space. By the 1950s the company held about 176 patents, including Revacycle, which cuts straight bevel gears in one pass with a single broach-like cutter, the Curvic coupling, and Coniflex for straight bevel gears (from the 1940s)^[4][27]. The company history says its best-selling machines were the No.116 generator for cutting hypoid pinions and the No.606/607 Formate machines for roughing and finishing the ring gears, and that automakers around the world installed them in rows^[4]. The ring gears were cut without generating, by form cutting (Formate), a method suited to mass production^[27].

In 1972 the theory of "completing" was established, allowing bevel gears that had been cut in five separate operations to be cut in a single operation, in 25% of the time. Machines such as the No.645 of 1974 had higher rigidity and produced helical motion and tilt with change gears and cams^[4]. The company built a tool plant in Plymouth, England, in 1966, listed on the New York Stock Exchange in 1968, built a plant in Belgium in 1971, and in 1972 received an order for 79 machines from China^[4].

Standards and education

After the war AGMA developed standards for gear accuracy. AGMA 390.01 and 390.02 of 1961–64 used quality grades in which a larger number meant higher precision (a convention later reversed)^[39]. In 1958 the first "Gear School" (a course in gear theory and manufacturing) was held at Barber-Colman in Rockford; according to Gleason's company history, Gleason Cutting Tools still continues it today^[4]. In the same year, 1958, Robert S. Woodbury of MIT published History of the Gear-Cutting Machine. It is a technical history of gear cutting machines that drew on Brown & Sharpe's internal documents, and the book this chapter relies on most^[2].

The NC wave and foreign machines

NC came to gear cutting machines later than to lathes and milling machines, because hob and blank, or cutter and blank, must keep turning in a fixed ratio. In 1975 Germany's Pfauter showed the first NC hobbing machine at EMO in Paris, and in 1983 it brought out the CNC hobbing machine PE150^[19]. The first issue of the trade journal Gear Technology, launched in May/June 1984 by Randall Publishing of Elk Grove Village, Illinois, carried an advertisement by American Pfauter, Pfauter's US company, for CNC hobbing machines, CNC gear measuring machines and gear grinders with CBN wheels^[44]. In cylindrical gear cutting machines, the era had come when German machines entered American factories.

Old American firms also changed shape. Loyd Koch and Larry Bourn, engineers at Sundstrand, began rebuilding machines in 1971 and founded Bourn & Koch in Rockford in 1975^[43]. In 1985 the company bought Barber-Colman's machine tool division, taking over its hobbing machine designs, spare parts and service^[45]. Gleason was reorganized as Gleason Corporation in 1984^[4].

★CNC and consolidation (1988 onward)

PHOENIX: the bevel gear machine that did away with gear trains

Mechanical bevel gear generators produced the roll ratio, cutter position, helical motion and so on with many change gears, cams and shafts. Unveiled by Gleason in 1988, PHOENIX was a 6-axis CNC machine, developed over more than five years, that did away with all these gear trains, shafts and handles and produced each motion with its own small motor. The company history says setup times became shorter and the same machine could be used for both cutting and grinding^[4]. In the early 1990s the range expanded and "Power Cutting," which cuts fast with carbide blades without cutting oil, was developed, and in 1995 came UMC (Universal Motion Concept), for grinding quiet gears^[4].

Consolidation by Gleason

In the late 1990s Gleason moved boldly into cylindrical gear machines. It acquired Hurth Maschinen und Werkzeuge of Munich (shaving, grinding and honing machines) in 1995 and, in 1997, the group of Hermann Pfauter of Germany, the major hobbing machine maker^[4][19]. Thus Gleason, the bevel gear company, came to cover cylindrical gear hobbing, shaping, shaving, grinding and honing as well. In 2000 it became private again, and Pfauter-Maag Cutting Tools near Rockford became Gleason Cutting Tools Corporation. In 2005 it bought M&M Precision Systems of Dayton, Ohio, a gear measuring machine maker, renaming it Gleason Metrology Systems, and in 2006 it launched the Genesis series of cylindrical gear production machines^[4]. In 2012 it sold its first power skiving machine (skiving is covered in detail in the German chapter), and it added the gear design software KISSsoft in 2017 and Faessler's gear honing business in 2019^[4].

The end of Fellows, and Bourn & Koch

The founder, E. R. Fellows, remained president until his death in May 1945^[36][37]. The company was bought by Emhart in 1974 and later became a subsidiary of Boston's Goldman Industrial Group^[41][42]. Then, in 2002, Fellows came to an end. According to Gear Technology, its parent, Goldman Industrial Group, entered bankruptcy proceedings, and Fellows Corp. in North Springfield ceased operations on February 13. Jones & Lamson, Bryant Grinder and others in the same group also closed^[13]. In an editorial the magazine wrote that it hoped someone would buy Fellows and keep the name alive^[13]. Within the year, Bourn & Koch of Rockford took over the Fellows gear shaper line, complete with drawings and documents, and later also developed a new model of Fellows gear shaper^[43][46]. It also rebuilds old mechanical Model 10-4 machines as CNC machines^[43].

The direction of the standards reverses

AGMA's accuracy standard was unified in ANSI/AGMA 2000-A88 of 1988 as "Q" numbers (larger is more precise), but from ANSI/AGMA 2015-1-A01 of 2001 it switched to the ISO convention, in which a larger number means a coarser grade (the reverse of the old Q numbers)^[39]. When reading the grades on old drawings, always check which edition of the standard applies (see the accuracy section of "Gear study").

Today's Players

Gear machine and tool companies based in the United States today include Gleason of Rochester (bevel and cylindrical gear machines, tools and measuring machines), Bourn & Koch of Rockford (which carries on Barber-Colman's hobbing machines and Fellows's gear shapers), and Star Cutter, founded in 1927 (hobs, pinion cutters, shaving cutters, skiving cutters and hobbing machines; sales and service by Star SU)^{[4][45][46][47]}. Today's gear machine and tool makers are listed in Makers of gear cutting tools and gear machines, and how to use each tool is covered on the hob, pinion cutter, shaving cutter, skiving cutter pages.

What it means on the shop floor. When looking at a used gear machine, check whether indexing is by change gears or by CNC electronic gearing, whether the shaper's helix requires changing the helical guide, and whether a bevel gear machine is mechanical (change gears and cams, as on the No.116) or a CNC machine of the PHOENIX generation or later; this tells you how much setup work it needs and what jobs it is good at. Old Fellows and Barber-Colman machines are still rebuilt and used today.

Links with Japan

Gear cutting in Japan began with American machines. According to Toshio Aida's A Technical History of Gears, an automatic gear cutter from Gould & Eberhardt (US) was bought in Japan in 1901 and an automatic gear cutter from Cincinnati in 1903, raising the productivity and accuracy of gear cutting. For bevel gears, Gleason generating-type bevel gear cutters went to Kisha Seizo (a locomotive maker) and Ikegai Iron Works in 1915–16, and bevel gears began to be cut by the generating method in Japan as well. Among private gear-cutting shops, there was even one that bought a hobbing machine in 1920 and went on to assemble Gleason bevel gear cutters, Fellows gear shapers and German hobbing machines^[20] (Japanese Archive, Chapter 4 timeline).

After the war, American finishing technology arrived along with mass production of automobile gears. Fujikoshi Steel Industry (today's Nachi-Fujikoshi), seeing that Japanese automakers had installed shaving machines but struggled to get replacement cutters, formed a technical tie-up with Michigan Tool (US) for shaving cutter manufacturing in November 1953^[38]. Even so, a 1968 survey by the Japan Society for the Promotion of Machine Industry noted that, of domestic machine tool demand, gear cutting machines and gear finishing machines depended most on foreign machines, that few spiral bevel gear cutters were available commercially in Japan, and that Gleason (US) was world-famous^[40].

Later, Japanese makers advanced with their own technology to hobbing machines, gear grinders and dry cutting (Japanese Archive, Chapter 4). On Gleason's side, it invested in Japan's OGA Corporation in 1994 and made it a wholly owned subsidiary in 1999 (today's Gleason Asia), and in 2013 Saikuni Machinery, a rack machining machine maker in Niigata, joined the group^[4].

FAQ

What are Gleason and Fellows each known for?

Gleason (1865, Rochester) is a bevel gear cutting machine company, known for the bevel gear planer of 1874, the automatic bevel gear generator of 1898, the spiral bevel gear of 1913, the hypoid gear of the 1920s, and the CNC machine PHOENIX of 1988. Fellows (1896, Springfield, Vermont) made practical the gear shaper, which cuts teeth with a gear-shaped pinion cutter, and its machine spread worldwide as the way to cut internal gears.

Who built the first hobbing machine in America?

The first hobbing machine certainly put to actual use is said to be George B. Grant's machine (applied 1887, US Patent 405,030 in 1889). However, it was Germany's Pfauter (German patent 1897, US Patent 640,728 in 1900) who established the basis of today's hobbing machine by tilting the hob axis by the helix angle and using a differential to cut helical gears too, and American makers followed.

When and why did hypoid gears spread?

Gleason's Ernest Wildhaber conceived them in 1924. Because the pinion axis is offset from the center of the gear, the propeller shaft can be lowered and the car body brought down by 50 mm or more. According to Gleason's materials, the 1927 Packard 426 was the first production car with them, and within a few years the major automakers had adopted them for their rear axles.

Does the Fellows company still exist?

Fellows Corp. ceased operations in February 2002 after its parent went bankrupt. The same year, Bourn & Koch of Rockford took over the Fellows gear shaper line along with its drawings, and it continues to develop new models and convert old machines to CNC.