Jo-block

engineering

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July 17, 2026

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A "Jo block," also known as a Johansson block, is a set of precision measuring tools. These blocks are ground to an extremely high accuracy, often to within one hundred-thousandth of an inch or even better. They are named after C. E. Johansson, a Swedish engineer who developed them in the 20th century. Jo blocks are essential in engineering and manufacturing for precise measurements and calibration.1

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Carl Edvard Johansson
Johansson’s blocks, known as “Jo-blocks,” were made of the highest quality steel and were fabricated to a precision that made them famous around the world. From 1925 to 1936 he worked in Dearborn, Mich., under exclusive contract to Henry Ford, who used his blocks and also sold them to…
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Johansson’s blocks, known as “Jo-blocks,” were made of the highest quality steel and were fabricated to a precision that made them famous around the world. From 1925 to 1936 he worked in Dearborn, Mich., under exclusive contract to Henry Ford, who used his blocks and also sold them to…
Read More