Manufactured Gage Blocks (AKA Jo Blocks) used in manufacturing precision metalworking machinery. They were invented by Carl Edvard Johansson in 1897 and patented in Sweden on 02 May 1901. The first set imported to the U. S. was sold to Henry M. Leland at the Cadillac Automobile Co. The firm established a U. S. manufacturing firm in Poughkeepsie, NY and in 1918 the company was sold the Ford Motor Co. Ford moved the company to Dearborn, MI and continued manufacturing Gage Blocks there.
Note: Even though this firm did not manufacture machinery, it provided the basic building blocks to enable other firms to manufacture them with the necessary precision to be successful.
"Johansson gage blocks, now the finest inspection measuring device manufactured, are, like many other implements used in modern manufacture, the product of war needs. C. E. Johansson, a Swedish engineer, was employed in the Swedish government arsenal, and had charge of making all kinds of jigs, special tools and machinery necessary to put the arsenal on the interchangeable parts system of production. He quickly realized that the cost of making master gages for all parts would be prohibitive on account of the change in size limits and in designs from time to time, and he evolved the idea of making the least number of gages to obtain accurate measurement for the greatest possible number of sizes.
After working out a combination of key sizes whereby any multiple of .0001 part of an inch could be obtained through the addition or subtraction of the various units of the key, Johansson started out to solve the problem of making accurate block gages to the exact dimensions necessary for this key system. His solution of this problem has made him famous, and has been one of the most remarkable developments in the improvement of the manufacturing industries of the world.
The first part of the problem was to make an absolutely flat surface upon a block of steel. The second step consisted of making two flat surfaces parallel, and the third in making two flat surfaces parallel and a certain distance apart. Written down in this simple fashion, it seems quite easy, but let anyone who thinks thus try to file ten pieces of steel to exact one-inch cubes and get them so accurate that while each dimension measures precisely one inch, the ten blocks piled one on the other will practically cohere and make one piece of steel ten inches long.
Johansson started to solve this problem in 1889. His first combination set of gages was not ready until 1897, and even then one of the greatest difficulties remained to be solved, viz.: The treating of the steel so as to minimize expansion and contraction regardless of time. Johansson experimented for nine years with this part of the problem and it was not until 1906 that he succeeded in making the first combination set which could be guaranteed in accuracy to within .00001 part of an inch.
When he started to make his combination set, his intentions were to make working gages for the tool maker and inspector, but when the blocks were completed they were so accurate that they became standards, and five years later, viz.: in 1911, facilities were completed for manufacturing the blocks and a company was organized with Johansson as leader for putting them on the market on a production basis.
At first these gages met with prejudice and many mechanics considered them merely a curiosity. Scientists pronounced them impossibilities, and when they were first demonstrated at the International Bureau in Paris, Professor Benoit said, "This is pure magic and nonsense—you gentlemen don't know what you are talking about." But in spite of prejudice and ridicule, these gages have slowly found their way into the mechanical industries of the world, and are today practically the standards in settling all disputes about sizes and in accurately checking tools and gages; in fact, they are the toolmakers' delight and inspectors' authority.
A story is. told of a tool contractor in Dayton, who had made a very elaborate fixture for a Detroit automobile plant. A few days after delivery he received word that it had been rejected. The contractor knew that he was right because the fixture in question was made in accordance with Johansson gages. Putting the gages under his arm he took the next train for Detroit. At the plant of his customer he was told that the fixture had been checked with micrometers and found not to be up to specifications. The tool contractor checked the fixture with his set of Johansson gages and it was shown to be perfectly correct. The chief inspector was very much embarrassed and immediately insisted that the manager equip him with a set of Johansson gages so that he would be protected against any future mistakes of that nature.
Johansson gages are made both for the English and metric systems. The surfaces are so perfect that when placed together they practically cohere as one piece of metal. In an experiment two one-inch blocks, on which the area of the end surfaces is .516 of a square inch, the lower block supported 220 pounds without separating from the upper block.
The blocks are finished in what is known as the "Johansson Lapped Surface." This surface is so perfect that its reflecting properties are equal to those of the best French plate glass. Under the microscope the surface edge, after being finished by Johansson lapped process, appears almost like a straight line, whereas the edge of ordinary lapped steel under the same microscope makes a very ragged line. The Johansson blocks are self-checking and the exactness of measurement is carried to such a pitch that English measurement can be checked against blocks manufactured for the metric system. The one-inch block checks perfectly against 25.4 millimeters built up with three or any number of blocks.
In numerous manufacturing establishments where interchangeability of parts is a very important consideration, all gages and jigs used in manufacturing processes are checked by the use of Johansson blocks. In the setting of sine bar fixtures, and in arranging the heights of pads for milling processes, in the setting of minimeters and in the gaging and checking of all straight surfaces, these Johansson blocks are practically indispensable." (Quote from 1919 lecture by Ernst Mentor)
See also the Swedish branch of CEJ
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