The Quest For Roundness That Changed Precision Machining Forever
Trade Archive
21,563 views
On October 14th, 1943, 291 B-17s of the US Eighth Air Force flew deep into Germany to destroy a cluster of factories in Schweinfurt. 60 were shot down, and around 600 airmen were lost. 2 months earlier, the first raid on the same town had cost another 60. The target was the ball bearing, and behind it, the hardest problem in the part: making millions of steel balls perfectly round and exactly the same size.
This documentary traces that problem from English workmen shaping balls on foot-powered lathes around 1870, to Friedrich Fischer's 1883 grinding machine in Schweinfurt, whose wheel was tilted 1.9 degrees so every ball kept rolling onto a new axis and wore down only its high spots. That idea turned a small Bavarian town into the capital of the ball bearing. It covers the American ball makers of Fitchburg, Bangor and Cleveland, Frederick Winslow Taylor's famous study of the women who inspected steel balls on the backs of their hands, Henry Timken's tapered roller bearing and the Canton company that put it under 90 percent of North American vehicles, Fafnir's fight against German imports in New Britain, and Sven Wingqvist's self-aligning bearing, born in a Gothenburg textile mill built on shifting clay.
It follows the Allied planners who ranked ball bearings second and grinding wheels fourth on their list of German targets, the two raids of August 17th and October 14th, 1943, and what happened afterward: the Eighth Air Force's loss of air superiority, Germany's dispersal of the industry, neutral Sweden's role on both sides, the motor gunboats that ran bearings to Britain, the Mosquito flights that carried Niels Bohr in a bomb bay, and the post-war survey that found no measurable effect on essential German war production.
The story continues through Schweinfurt's rebuilding, the rise of Japanese competition, FAG's hostile takeover in 2001, the counterfeit bearing trade, and SKF's decision in September 2026 to split its Schweinfurt plant in two. Along the way it explains how a modern ball is made, from wire cut and struck into a rough sphere under about 10 tonnes of force, through hardening, grinding and lapping, to grade 3 balls that are round within 3 millionths of an inch and sorted into lots by tenths of a micron. It also covers the silicon nitride ceramic balls that went into machine-tool spindles and the Space Shuttle main engine. It ends with the Gravity Probe B gyroscope rotors, the roundest objects ever manufactured, polished with the same principle Fischer found in 1883.
Subscribe to Trade Archive for more documentaries on the tools, machines and trades that built the modern world.
Sources
Chiles, James R. "Small Wonder: The Magnificent Ball Bearing." Invention & Technology, Summer 1985.
Commercial Motor. "The Making of Balls for Bearings." October 3, 1912.
Correll, John T. "The Cost of Schweinfurt." Air & Space Forces Magazine, February 2010.
Craven, Wesley Frank, and James Lea Cate, eds. The Army Air Forces in World War II. Vol. 2, Europe: Torch to Pointblank. Chicago: University of Chicago Press, 1949.
Encyclopedia.com. "FAG Kugelfischer Georg Schäfer AG." International Directory of Company Histories.
Federal Trade Commission. "FTC Imposes Conditions on Acquisition of FAG Kugelfischer Georg Schäfer AG by INA Holding Schaeffler KG." December 20, 2001.
Golson, Eric B. "Did Swedish Ball Bearings Keep the Second World War Going? Re-evaluating Neutral Sweden's Role." Scandinavian Economic History Review 60, no. 2 (2012).
Grant, Robert H. The Manufacture of Steel Balls. Machinery's Reference Series 116. New York: Industrial Press, 1914.
Harvey, A. D. "Sir Arthur Harris and Panacea Targets." Air Power History, 2014.
Haus der Bayerischen Geschichte. "Schweinfurt." Wiederaufbau in Bayern.
Mainfranken News. "Aus einem werden zwei: SKF trennt Automobil- und Industriegeschäft in Schweinfurt auch räumlich." September 16, 2026.
National Institute of Standards and Technology. "Kilogram: Silicon Spheres and the International Avogadro Project."
National Museum of the United States Air Force. "Black Thursday: Schweinfurt, October 14, 1943." Fact sheet.
Schaeffler Tomorrow. "Impeccable: Round and Smooth." December 2023.
Stanford University. "Gravity Probe B: Extraordinary Technologies."
Taylor, Frederick Winslow. The Principles of Scientific Management. New York: Harper & Brothers, 1911.
Tekniska museet. "Sven Wingquist: Spherical Ball Bearings." Stockholm.
Time. "Foreign Trade: Backfire." May 29, 1944.
United States Department of State. Foreign Relations of the United States, 1944. Vol. 4, Europe. Washington, DC: Government Printing Office.
United States Strategic Bombing Survey. Summary Report (European War). Washington, DC: Government Printing Office, 1945.
United States Strategic Bombing Survey. The German Anti-Friction Bearings Industry. Washington, DC, 1947.
8 Comments
The Quest For Roundness That Changed Precision Machining Forever
Trade Archive
21,563 views
On October 14th, 1943, 291 B-17s of the US Eighth Air Force flew deep into Germany to destroy a cluster of factories in Schweinfurt. 60 were shot down, and around 600 airmen were lost. 2 months earlier, the first raid on the same town had cost another 60. The target was the ball bearing, and behind it, the hardest problem in the part: making millions of steel balls perfectly round and exactly the same size.
This documentary traces that problem from English workmen shaping balls on foot-powered lathes around 1870, to Friedrich Fischer's 1883 grinding machine in Schweinfurt, whose wheel was tilted 1.9 degrees so every ball kept rolling onto a new axis and wore down only its high spots. That idea turned a small Bavarian town into the capital of the ball bearing. It covers the American ball makers of Fitchburg, Bangor and Cleveland, Frederick Winslow Taylor's famous study of the women who inspected steel balls on the backs of their hands, Henry Timken's tapered roller bearing and the Canton company that put it under 90 percent of North American vehicles, Fafnir's fight against German imports in New Britain, and Sven Wingqvist's self-aligning bearing, born in a Gothenburg textile mill built on shifting clay.
It follows the Allied planners who ranked ball bearings second and grinding wheels fourth on their list of German targets, the two raids of August 17th and October 14th, 1943, and what happened afterward: the Eighth Air Force's loss of air superiority, Germany's dispersal of the industry, neutral Sweden's role on both sides, the motor gunboats that ran bearings to Britain, the Mosquito flights that carried Niels Bohr in a bomb bay, and the post-war survey that found no measurable effect on essential German war production.
The story continues through Schweinfurt's rebuilding, the rise of Japanese competition, FAG's hostile takeover in 2001, the counterfeit bearing trade, and SKF's decision in September 2026 to split its Schweinfurt plant in two. Along the way it explains how a modern ball is made, from wire cut and struck into a rough sphere under about 10 tonnes of force, through hardening, grinding and lapping, to grade 3 balls that are round within 3 millionths of an inch and sorted into lots by tenths of a micron. It also covers the silicon nitride ceramic balls that went into machine-tool spindles and the Space Shuttle main engine. It ends with the Gravity Probe B gyroscope rotors, the roundest objects ever manufactured, polished with the same principle Fischer found in 1883.
Subscribe to Trade Archive for more documentaries on the tools, machines and trades that built the modern world.
Sources
Chiles, James R. "Small Wonder: The Magnificent Ball Bearing." Invention & Technology, Summer 1985.
Commercial Motor. "The Making of Balls for Bearings." October 3, 1912.
Correll, John T. "The Cost of Schweinfurt." Air & Space Forces Magazine, February 2010.
Craven, Wesley Frank, and James Lea Cate, eds. The Army Air Forces in World War II. Vol. 2, Europe: Torch to Pointblank. Chicago: University of Chicago Press, 1949.
Encyclopedia.com. "FAG Kugelfischer Georg Schäfer AG." International Directory of Company Histories.
Federal Trade Commission. "FTC Imposes Conditions on Acquisition of FAG Kugelfischer Georg Schäfer AG by INA Holding Schaeffler KG." December 20, 2001.
Golson, Eric B. "Did Swedish Ball Bearings Keep the Second World War Going? Re-evaluating Neutral Sweden's Role." Scandinavian Economic History Review 60, no. 2 (2012).
Grant, Robert H. The Manufacture of Steel Balls. Machinery's Reference Series 116. New York: Industrial Press, 1914.
Harvey, A. D. "Sir Arthur Harris and Panacea Targets." Air Power History, 2014.
Haus der Bayerischen Geschichte. "Schweinfurt." Wiederaufbau in Bayern.
Mainfranken News. "Aus einem werden zwei: SKF trennt Automobil- und Industriegeschäft in Schweinfurt auch räumlich." September 16, 2026.
National Institute of Standards and Technology. "Kilogram: Silicon Spheres and the International Avogadro Project."
National Museum of the United States Air Force. "Black Thursday: Schweinfurt, October 14, 1943." Fact sheet.
Schaeffler Tomorrow. "Impeccable: Round and Smooth." December 2023.
Stanford University. "Gravity Probe B: Extraordinary Technologies."
Taylor, Frederick Winslow. The Principles of Scientific Management. New York: Harper & Brothers, 1911.
Tekniska museet. "Sven Wingquist: Spherical Ball Bearings." Stockholm.
Time. "Foreign Trade: Backfire." May 29, 1944.
United States Department of State. Foreign Relations of the United States, 1944. Vol. 4, Europe. Washington, DC: Government Printing Office.
United States Strategic Bombing Survey. Summary Report (European War). Washington, DC: Government Printing Office, 1945.
United States Strategic Bombing Survey. The German Anti-Friction Bearings Industry. Washington, DC, 1947.
I would ask, however, "can someone please proofread the captions?" Too many misspellings for a piece talking about accuracy and precision.