ARCHIVE 03The Lineage of Grinding Machines

Modeled on Imports: Japanese Grinding Machines (Taisho–1945)

Domestic grinder production began with the "tool grinder", used to sharpen cutting tools. According to the company history of Okuma Iron Works (today's Okuma), in 1918 the company received drawings from an army arsenal and built the Type GA-1 tool grinder, modeled on the Norton (US) No. 1 universal tool grinder. This was the start of the company's grinder making^[2]. The following year, 1919, it also built internal grinders modeled on a Heald (US) product, but only three were made. In the late Taisho era it built the Type GA-2 universal tool grinder, modeled on the Brown & Sharpe (US) No. 13, and into the Showa era its main products remained the Type GAG and Type GM universal tool grinders^[2]. In the Taisho era Ikegai Iron Works also built almost every kind of machine tool, grinders included^[3].

Precision grinders themselves long had to be imported. The Lindner (Germany) thread grinder bought in 1936 by the gauge maker Kuroda Kyohan Seisakusho (today's Kuroda Precision Industries) is said to have been only the third in Japan, and cost more than the company's monthly output^[7].

Grinders for bearings and aircraft

In the late 1930s, as aircraft production was rushed, high-performance grinders ran short. In 1938 Okuma built the Kamiiida plant as a dedicated grinder factory^[2]. Under the 1939 National Mobilization research and testing order (a system under which the state ordered prototypes), Okuma built prototypes of various grinders in 1941–44, the best known being the Type GHU universal grinder. A hydraulic machine modeled on a Landis (US) grinder, it passed its acceptance review in October 1941^[3]; it could do cylindrical, internal and surface grinding, and 500 were built by 1945, laying the foundation for postwar grinder production^[10]. In the same year, 1939, Tsugami Seisakusho also completed the T-UG300 hydraulic universal cylindrical grinder with an incentive grant from the Ministry of Commerce and Industry^[9].

Mass production of bearings depends on the "centerless grinder", which grinds round parts continuously without centers to support them. NSK's company history says its prototype appeared in 1916^[1]. In Japan, Nisshin Kikai Seisakusho of Hamamatsu began making centerless grinders in 1940^[6], and in 1939–40 NSK designed its own special grinders for bearings (centerless grinders for roller outer diameters, and grinders for flanges and grooves). In 1942, on the instructions of the Ministry of Commerce and Industry, domestic production of special bearing grinders was pushed forward, and surface grinders, internal grinders and ball-bearing groove grinders came to be made in Japan^[1].

Main types of grinding machines. The cylindrical grinder grinds the outside of round shafts (one whose wheel head can swivel to grind bores as well is a universal grinder); the internal grinder grinds the inside of holes; the surface grinder grinds flat surfaces; and the centerless grinder grinds parts while turning them between two wheels, without supporting them on centers. There are also special grinders for set shapes such as gears, threads, cams and tool cutting edges.

Cylindrical, Surface, Internal and Centerless Grinders Arrive (1945–1970)

After the war, grinder makers started over. Nisshin Kikai Seisakusho was dissolved once due to war damage, made a fresh start as Nisshin Shokki in 1947, and resumed making centerless grinders in 1950^[6]. In Kitakyushu, Mitsui High-tec built its first surface grinder in 1950 by combining parts from used machines; it was the first machine the company built itself^[11].

In surface grinders, Okamoto Machine Tool Works developed the Type PSG-6 in 1953, which it calls Japan's first domestically made surface grinder. It followed with the IGM series of internal grinders in 1954 and the OGM series of cylindrical grinders in 1969^[4]. Also in 1953, Kuroda Kyohan Seisakusho developed the horizontal-spindle surface grinder GS-201 for its own die and mold making. It was installed in many die shops, and in response to outside demand it went on general sale in 1963^[7][12]. Kuroda was renamed Kuroda Precision Industries in 1965, and in the same year, through a tie-up with Diaform of the UK, released a surface grinder with a built-in device for shaping the wheel^[7]. In 1963 Mitsui High-tec developed the MSG-1, a surface grinder for manual profile grinding that could also grind cemented carbide^[22].

In cylindrical grinders, Shigiya, a loom maker in Fukuyama, began developing a combined universal and tool grinder in 1952, switched entirely to machine tool production in 1958, and completed the Type G-24 cylindrical grinder in 1959^[15].

Open the 1963 Kokusan kosaku kikai sogo katarogu (Comprehensive catalog of Japanese machine tools) and you find cylindrical grinders (Okuma Iron Works, Toyoda Machine Works and others), centerless grinders (Nisshin Kikai Seisakusho, Nippei Sangyo, Nippon Kenmaki), surface grinders and optical profile grinders (Okamoto Machine Tool Works) and tool grinders (Waida Seisakusho, Howa Sangyo), showing that all the main types of grinders were by then made in Japan^[20].

Precision and Mass Production: Bearings and Auto Parts (1954–1975)

What determines a grinder's accuracy is the bearing of the spindle that turns the wheel. Nagaoka Shinkichi of Okuma Iron Works developed the "Okuma non-circular plain bearing", which forms wedge-shaped oil films at three points around the spindle to raise rotational accuracy and stiffness. The Mechanical Engineering Heritage gives its development as 1954, while the National Museum of Nature and Science database gives 1943^[13][14].

1956: Type GPB cyclic cylindrical grinder

With government subsidies, Okuma built the Types GIR and GOR special grinders for ball-bearing grooves (FY1954) and the Types GCP-150 and GCP-250 cylindrical grinders (1955–56), and in March 1956 completed the Type GPB cyclic cylindrical grinder. It automatically performed roughing, finishing and sizing (measuring the size and stopping) in one continuous cycle, and drew attention at the 2nd Osaka International Trade Fair that year^[2]. About 700 of the Type GPB, which used the non-circular plain bearing, were built by 1969, achieving mirror-like finishes in mass production. In 2013 it was designated Mechanical Engineering Heritage No. 59 together with the bearing^[13].

Toyoda Machine Works and Gendron

Mass production of cars created new demand for grinders. In 1955 Toyoda Machine Works, spun off from Toyota Motor Co., signed a technical tie-up with Gendron of France for cylindrical grinders^[16]. Gendron's grinders used fluid bearings, a mechanism unlike that of domestic machines at the time, and there were worries inside the company, but according to the company history it went ahead after explaining the deal to the head of the industry association and to Okuma's president as well^[17]. Its first grinder, the Toyoda-Gendron cylindrical grinder RA25-100, was shown at a trade fair in 1956 and attracted interest with its hydrostatic fluid bearings; it supported the auto industry in jobs such as grinding crankshaft journals^[18][17].

Strong sales changed how the machines were built, too. Toyoda-Gendron orders reached 350 within three years of launch, and in August 1961 Toyoda Machine Works completed a conveyor line for assembling grinders and began building LG grinders at 40 a month (the company calls it a "world first")^[21]. In 1965 it ended the tie-up with Gendron and announced its own "TOYODA grinders"^[17], and in 1966 it independently built the Type GCA, a fully automatic cam grinder in a field that foreign makers had monopolized. With its own high-rigidity fluid bearings it matched or exceeded the accuracy of foreign machines, and many went to automakers^[24].

Centerless grinders also became faster and automatic. In 1970 Nisshin Kikai Seisakusho exhibited the Type HI-GRIND 2 hydrostatic high-speed centerless grinder, which floats both its bearings and its guideways on oil pressure, at the 5th Japan International Machine Tool Fair, and in 1973 it went into full production of fully automatic centerless grinders with gauges that measure size while grinding^[6].

NC Grinding Machines (1964–1990)

Grinders went NC a little later than lathes and milling machines. At the 2nd Japan International Machine Tool Fair in October 1964, Okuma exhibited the Type GCS-N numerically controlled cylindrical grinder, fitted with the OSP200 NC unit it had developed itself. It drew attention as an NC unit developed by a machine tool maker on its own^[2]. In the same year, Toyoda Machine Works released the GCN15 numerically controlled cam grinder^[21].

The NC machine tool catalog compiled by the Japan Machine Tool Builders' Association in 1968 lists Nippei Sangyo's CGK-NC numerically controlled cylindrical grinder (with Fujitsu's FANUC NC unit), and from Toyoda Machine Works the GCN15-100 numerically controlled cam grinder, the GUN20-100 multipurpose numerically controlled grinder with simultaneous control of three axes (wheel head, table and work head), and the GCN400V numerically controlled cam profile grinder^[23]. Also in 1968, Okamoto Machine Tool Works developed the Type NFG-5 CNC surface and profile grinder (the company calls it a "world first")^[4].

From the 1970s, large, high-precision NC grinders increased, partly through foreign technology. Through a technical tie-up with Berthiez of France, OM Ltd. introduced the VGM-125 vertical grinder with NC in 1971 and acquired the skills to achieve submicron accuracy^[25]. Waida Seisakusho began producing CNC profile grinders in 1978 and CNC jig grinders in 1982^[19], and Shigiya Seiki Seisakusho completed its first CNC cylindrical grinder, the GN-27, in 1980^[15]. OM Ltd.'s 1985 double-column surface grinder PGD-1308 fed its table with ball screws rather than hydraulics to limit heat, and ran a fully automatic grinding cycle once the values were entered^[27].

Toyoda Machine Works' 1990 CNC general-purpose cylindrical grinder GL4 had a learning function that set grinding conditions automatically once drawing data were entered (the company calls it a world first for grinders)^[21]. In the same year Taiyo Koki, founded in Nagaoka in 1986, began selling vertical grinders, which later became its main products^[28].

★CBN, High-Speed Grinding, Ultra-Precision and Multitasking Grinding (1970–)

Turn the wheel faster and you remove more material in the same time. Tsugami Seisakusho's 1971 product brochure lists the PG350 precision high-speed cylindrical grinder, which raised the wheel peripheral speed from 1,800 m/min (30 m/s) to 3,600 m/min (60 m/s), for mass production of automobile parts and the like^[9].

CBN wheels

Wheels of CBN (cubic boron nitride), second in hardness only to diamond, grind hardened steel well, which diamond does poorly. Around 1972 at Toyoda Machine Works, an engineer who had been researching diamond wheels under the guidance of the Tokyo Institute of Technology obtained CBN grains and began applying them to cam grinding. The resulting CBN production cam grinder received the Japan Society for the Promotion of Machine Industry Award in October 1977^[17]. Toyoda Machine Works began producing CNC/CBN cylindrical grinders in 1980^[16], and from around 1984 moved its grinders fully to CNC and CBN^[21]. In 1985 it began developing a masterless cam grinder that grinds cam profiles by CNC without master cams^[17], and Shigiya Seiki Seisakusho also released the GCM-30 CNC masterless cam grinder in 1996^[15].

Ultra-precision and multitasking grinding

From the 1980s, ultra-precision grinders that grind brittle materials such as ceramics, glass and silicon to nanometer accuracy became more common. Nisshin Kikai Seisakusho developed an ultra-precision grinder for ceramics in 1983, the Type UG-1000, a production-ready ultra-precision centerless grinder, in 1985, and the "Nanotron", a small nanometer-class centerless grinder, in 1987^[6]. OM Ltd.'s SFG ultra-precision vertical-spindle surface grinder (2001) grinds HDD glass substrates and silicon wafers without damaging them by keeping the grinding force constant^[31]. In 2007 Okamoto Machine Tool Works completed the UDG10035NC, an ultra-precision double-column surface grinder with hydrostatic guideways that it calls one of the largest of its kind in the world^[4].

"Multitasking", one machine handling several kinds of grinding, also advanced. Osaka Kiko's HPV400-GC (1992) is a grinding center that brought the versatility of the machining center to grinding, handling everything from ceramics and glass to carbide and hardened steel^[29]. In 2010 Shigiya Seiki Seisakusho developed the GAV-10 and GAV-15, vertical CNC angular cylindrical grinders that support the workpiece between centers at both ends (the company calls them a first in Japan)^[15], and in 2014 came Okamoto Machine Tool Works' UGM360NC CNC precision multitasking cylindrical grinder and Taiyo Koki's CVG series of vertical multitasking grinders^[4][28].

What it means on the shop floor. What today's grinders take for granted (hydrostatic bearings and guideways floating on oil or air, in-process gauges that measure size while grinding, CNC, CBN wheels, and dressers that shape the wheel) was added one item at a time on the machines of the 1950s–80s described here. When you read the specs of a used grinder or an old drawing, ask "What kind of bearings does it have?", "Does it have an in-process gauge?" and "Is the wheel speed high enough for CBN?" and you can tell which generation the machine belongs to.

⚒Grinders for Gears, Threads and Tools (1930–)

1930: Okamoto's Type ASG-2 spur gear grinder

Domestic production of special grinders for set shapes also began before the war. On an order from the Kure Naval Arsenal, Okamoto Machine Tool Works began design work and in 1930 completed the Type ASG-2, the first spur gear grinder made in Japan. It could grind gears up to 500 mm pitch diameter, 200 mm face width and module 8, and by changing gears it could handle different numbers of teeth. Thirteen were built by the end of the war, and this development led Okamoto to grow into a full-line grinder maker. One machine kept at the Nippon Institute of Technology Museum of Industrial Technology (nameplate dated 1941) is considered the oldest surviving Japanese-made spur gear grinder, and in 2021 it became Mechanical Engineering Heritage No. 106^[5][4].

Gear grinders then moved toward methods that match the wheel and gear profiles by CNC. In 1994 Mitsubishi Heavy Industries commercialized the ZG400, a CNC form gear grinder using electroplated CBN wheels, and reported JIS grade 0 accuracy on helical gears up to 400 mm outside diameter^[30]. For how gears themselves are cut, see Gear machining methods.

Thread grinders

Before the war, thread grinders for grinding thread gauges and tap threads had to be imported. Herbert Lindner (Germany) thread grinders Types FS1 and FS2, bought in 1937, were used to grind thread gauges, taps and thread-rolling dies, and still survive in Seki, Gifu Prefecture^[8].

Tool grinders

As carbide tools spread, demand grew for grinders to sharpen cutting edges. Waida Seisakusho began producing carbide tool bit grinders in 1956, and expanded to profile grinders in 1968, periphery grinders for indexable inserts (throwaway inserts) in 1974, and CNC fully automatic universal tool grinders in 1997^[19]. Insert peripheries used to be copy-ground with a cam made for each insert shape, but in 1980 Kobayashi Kikai Seisakusho developed the TAG-15, a periphery grinder that grinds by NC without cams (the company calls it a world first)^[26].