![Herbert Hoffmann GmbH, Trolley model](https://upload.wikimedia.org/wikipedia/commons/d/dc/Herbert_Hoffmann_GmbH%2C_Trolley_model.jpg)
Gauge blocks (also known as gage blocks, Johansson gauges, slip gauges, or Jo blocks) are a system for producing precision lengths. The individual gauge block is a metal or ceramic block that has been precision
ground
Ground may refer to:
Geology
* Land, the surface of the Earth not covered by water
* Soil, a mixture of clay, sand and organic matter present on the surface of the Earth
Electricity
* Ground (electricity), the reference point in an electrical c ...
and
lapped
Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine.
Lapping often follows other subtractive processes with more aggressive material removal as a first step ...
to a specific thickness. Gauge blocks come in sets of blocks with a range of standard lengths. In use, the blocks are stacked to make up a desired length (or height).
An important feature of gauge blocks is that they can be joined together with very little dimensional uncertainty. The blocks are joined by a sliding process called ''wringing'', which causes their ultra-flat surfaces to cling together. A small number of gauge blocks can be used to create accurate lengths within a wide range. By using three blocks at a time taken from a set of 30 blocks, one may create any of the 1000 lengths from 3.000 to 3.999 mm in 0.001 mm steps (or .3000 to .3999 inches in 0.0001 inch steps). Gauge blocks were invented in 1896 by Swedish machinist
Carl Edvard Johansson
Carl Edvard Johansson (1864–1943) was a Swedish inventor and scientist.
Johansson invented the gauge block set, also known as "Jo Blocks" ("Johansson gauge blocks"). He was granted his first Swedish patent on 2 May 1901, Swedish patent No. 170 ...
.
They are used as a reference for the calibration of measuring equipment used in
machine shop
A machine shop or engineering workshop (UK) is a room, building, or company where machining, a form of subtractive manufacturing, is done. In a machine shop, machinists use machine tools and cutting tools to make parts, usually of metal or plast ...
s, such as
micrometer Micrometer can mean:
* Micrometer (device), used for accurate measurements by means of a calibrated screw
* American spelling of micrometre
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; ...
s,
sine bar
A sine bar consists of a hardened, precision ground body with two precision ground cylinders fixed at the ends. The distance between the centers of the cylinders is precisely controlled, and the top of the bar is parallel to a line through the ce ...
s,
calipers, and
dial indicators (when used in an
inspection role). Gauge blocks are the main means of length standardization used by industry.
Description
![Gauge block interferometric length](https://upload.wikimedia.org/wikipedia/commons/e/e7/Gauge_block_interferometric_length.svg)
A gauge block is a block of metal or ceramic with two opposing faces ground precisely flat and parallel, a precise distance apart. Standard grade blocks are made of a hardened steel alloy, while calibration grade blocks are often made of
tungsten carbide
Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
,
chromium carbide or
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
because they are harder and wear less. Gauge blocks come in sets of blocks of various lengths, along with additional wear blocks, to allow a wide variety of standard lengths to be made up by stacking them. The length of each block is actually slightly shorter than the nominal length stamped on it, because the stamped length includes the length of one ''wring film'', a film of lubricant which separates adjacent block faces in normal use. The thickness of the wring film is about . The gauge's nominal length is also known as the ''
interferometric length''.
In use, the blocks are removed from the set, cleaned of their protective coating (
petroleum jelly
Petroleum jelly, petrolatum, white petrolatum, soft paraffin, or multi-hydrocarbon, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons (with carbon numbers mainly higher than 25), originally promoted as a topical ointment for its h ...
or oil) and ''wrung together'' to form a stack of the required dimension. Gauge blocks are
calibrated to be accurate at and should be kept at this temperature when taking measurements. This mitigates the effects of
thermal expansion
Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions.
Temperature is a monotonic function of the average molecular kinetic ...
. The wear blocks, made of a harder substance like
tungsten carbide
Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
, are included at each end of the stack, whenever possible, to protect the gauge blocks from being damaged in use.
Machinists and toolmakers try to use a stack with the fewest blocks to avoid accumulation of size errors. For example, a stack totaling .638 that is composed of two blocks (a .500 block wrung to a .138 block) is preferable to a stack also totaling .638 that is composed of four blocks (such as a .200, .149, .151, and .138 all wrung together). As detailed in the
Grades
Grade most commonly refers to:
* Grade (education), a measurement of a student's performance
* Grade, the number of the year a student has reached in a given educational stage
* Grade (slope), the steepness of a slope
Grade or grading may also r ...
section, each block has a size tolerance of a few millionths of an inch, so stacking them together introduces a cumulative uncertainty. However, the stacked error from even multiple blocks is usually negligible in all but the most demanding uses. In a busy shop, some of the blocks will be in use elsewhere, so one creates a stack from the blocks available at the time. Typically the few millionths of an inch difference will not be detectable, or matter, in the context. Contexts demanding ultimate precision are rarer and require additional expense (for example, more sets of blocks and higher grades of blocks).
Wringing
''Wringing'' is the process of sliding two blocks together so that their faces bond. Because of their ultraflat surfaces, when wrung, gauge blocks adhere to each other tightly. Properly wrung blocks may withstand a pull.
The mechanism is a combination of:
*
Vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...
applies pressure between the blocks because the air is squeezed out of the joint
*
Surface tension
Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to f ...
from oil and
water vapor
(99.9839 °C)
, -
, Boiling point
,
, -
, specific gas constant
, 461.5 J/( kg·K)
, -
, Heat of vaporization
, 2.27 MJ/kg
, -
, Heat capacity
, 1.864 kJ/(kg·K)
Water vapor, water vapour or aqueous vapor is the gaseous pha ...
that is present between the blocks
*
Molecular attraction
An intermolecular force (IMF) (or secondary force) is the force that mediates interaction between molecules, including the electromagnetic forces of attraction
or repulsion which act between atoms and other types of neighbouring particles, e.g. a ...
that occurs when two very flat surfaces are brought into contact; this force causes gauge blocks to adhere even without surface lubricants, and in a vacuum
It is believed that the last two sources are the most significant.
There is no
magnetism
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...
involved, although to a user the clinging together of the blocks feels a bit like weak refrigerator magnets sticking together. Unlike magnets, however, the cling only lasts while the blocks are completely joined—the blocks do not attract each other across any visible gap, as magnets would.
The process of wringing involves four steps:
#Wiping a clean gauge block across an oiled pad (see the
accessories section).
#Wiping any extra oil off the gauge block using a dry pad (see the
accessories section).
#The block is then slid perpendicularly across the other block while applying moderate pressure until they form a
cruciform
Cruciform is a term for physical manifestations resembling a common cross or Christian cross. The label can be extended to architectural shapes, biology, art, and design.
Cruciform architectural plan
Christian churches are commonly described ...
.
#Finally, the block is rotated until it is inline with the other block.
![Gauge block wringing](https://upload.wikimedia.org/wikipedia/commons/2/26/Gauge_block_wringing.svg)
After use, the blocks are re-oiled or greased to protect against
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
. The ability of a given gauge block to wring is called '; it is officially defined as "the ability of two surfaces to adhere tightly to each other in the absence of external means." The minimum conditions for wringability are a
surface finish
Surface finish, also known as surface texture or surface topography, is the nature of a surface as defined by the three characteristics of lay, surface roughness, and waviness.. It comprises the small, local deviations of a surface from the perf ...
of
AA or better, and a
flatness of at least .
There is a formal test to measure wringability. First, the block is prepared for wringing using the standard process. The block is then slid across a reference grade ( flatness) quartz
optical flat
An optical flat is an optical-grade piece of glass lapped and polished to be extremely flat on one or both sides, usually within a few tens of nanometres (billionths of a metre). They are used with a monochromatic light to determine the flatn ...
while applying moderate pressure. Then, the bottom of the gauge block is observed (through the optical flat) for oil or color. For Federal Grades 0.5, 1, and 2 and ISO grades K, 00, and 0 no oil or color should be visible under the gauge block. For Federal Grade 3 and ISO grades 1 and 2, no more than 20% of the surface area should show oil or color. This test is hard to perform on gauge blocks thinner than because they tend not to be flat in the relaxed state.
Accessories
![Endmaß Zange](https://upload.wikimedia.org/wikipedia/commons/0/05/Endma%C3%9F_Zange.jpg)
The pictured accessories provide a set of holders and tools to extend the usefulness of the gauge block set. They provide a means of securely clamping large ''stacks'' together, along with reference points, scribers, and various shapes of blocks that act like caliper jaws, either external or internal. Conical-tip ones ease measurement of center-to-center distances between hole centers. A stack of gauge blocks with external caliper-jaw accessories, all clamped together, acts as a quickly assembled custom-size
go or no-go gauge.
A special ''gauge block stone'' that cannot damage the surface is used to remove nicks and
burrs to maintain wringability.
There are two ''wringing pads'' used to prepare a gauge block for wringing. The first is an ''oil pad'', which applies a light layer of oil to the block. The second is a ''dry pad'', which removes any excess oil from the block after the oil pad has been used.
Grades
Gauge blocks are available in various grades, depending on their intended use. The grading criterion is tightness of tolerance on their sizes; thus higher grades are made to tighter tolerances and have higher
accuracy and precision
Accuracy and precision are two measures of ''observational error''.
''Accuracy'' is how close a given set of measurements ( observations or readings) are to their ''true value'', while ''precision'' is how close the measurements are to each oth ...
. Various grading standards include: JIS B 7506-1997 (Japan)/DIN 861-1980 (Germany), ASME (US), BS 4311: Part 1: 1993 (UK). Tolerances will vary within the same grade as the thickness of the material increases.
* reference (AAA): small
tolerance
Tolerance or toleration is the state of tolerating, or putting up with, conditionally.
Economics, business, and politics
* Toleration Party, a historic political party active in Connecticut
* Tolerant Systems, the former name of Veritas Software ...
(±0.05 μm) used to establish standards
* calibration (AA): (tolerance +0.10 μm to −0.05 μm) used to calibrate inspection blocks and very high precision gauging
* inspection (A): (tolerance +0.15 μm to −0.05 μm) used as
toolroom standards for setting other gauging tools
* workshop (B): large tolerance (tolerance +0.25 μm to −0.15 μm) used as shop standards for precision measurement
More recent grade designations include (U.S. Federal Specification GGG-G-15C):
* 0.5 – generally equivalent to grade AAA
* 1 – generally equivalent to grade AA
* 2 – generally equivalent to grade A+
* 3 – compromise grade between A and B
and ANSI/ASME B89.1.9M, which defines both absolute deviations from nominal dimensions and parallelism limits as criteria for grade determination. Generally, grades are equivalent to former U.S. Federal grades as follows:
* 00 – generally equivalent to grade 1 (most exacting flatness and accuracy requirements)
* 0 – generally equivalent to grade 2
* AS-1 – generally equivalent to grade 3 (reportedly stands for American Standard - 1)
* AS-2 – generally less accurate than grade 3
* K – generally equivalent to grade 00 flatness (parallelism) with grade AS-1 accuracy
The ANSI/ASME standard follows a similar philosophy as set forth in
ISO 3650
ISO is the most common abbreviation for the International Organization for Standardization.
ISO or Iso may also refer to: Business and finance
* Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007
* Iso ...
. See the NIST reference below for more detailed information on tolerances for each grade and block size. Also consult page 3 of
Commercial Gauge Block Tolerances(Length refers to the calibrated thickness)
Manufacture
Gauge blocks are usually made either from hardened alloy
tool steels,
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
s or
cemented carbide
Cemented carbides are a class of hard materials used extensively for cutting tools, as well as in other industrial applications. It consists of fine particles of carbide cemented into a composite by a binder metal. Cemented carbides commonly use ...
s (such as
tungsten carbide
Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
or
tantalum carbide
Tantalum carbides (TaC) form a family of binary chemical compounds of tantalum and carbon with the empirical formula TaC''x'', where ''x'' usually varies between 0.4 and 1. They are extremely hard, brittle, refractory ceramic materials with metall ...
). Often the
carbide
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.
Interstitial / Metallic carbides
The carbides of the ...
has a hardness of 1500
Vickers hardness
The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers test is often easier to use than other hardness t ...
. Long series blocks are made from high-quality steel having cross section (35 × 9 mm) with holes for clamping two slips together. These are also available in carbon steel material. Steel blocks are
hardened and
tempered. The
hardness
In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
is important because it slows down the gauge's rate of
wear
Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology.
Wear in m ...
during use (this is why other kinds of gauges, such as pins, thread plugs, and rings, are also hardened.) The cutting of the blocks to size is accomplished with
grinding
Grind is the cross-sectional shape of a blade.
Grind, grinds, or grinding may also refer to:
Grinding action
* Grinding (abrasive cutting), a method of crafting
* Grinding (dance), suggestive club dancing
* Grinding (video gaming), repetitive and ...
followed by
lapping
Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine.
Lapping often follows other subtractive processes with more aggressive material removal as a first step ...
.
Usually no plating or other coating is involved. Blocks are kept very lightly oiled, and are stored and used in dry climate-controlled conditions; unplated, uncoated steel gauge blocks can last for decades without rusting.
History
The gauge block set, also known as "Jo Blocks", was developed by the
Swedish
Swedish or ' may refer to:
Anything from or related to Sweden, a country in Northern Europe. Or, specifically:
* Swedish language, a North Germanic language spoken primarily in Sweden and Finland
** Swedish alphabet, the official alphabet used by ...
inventor
Carl Edvard Johansson
Carl Edvard Johansson (1864–1943) was a Swedish inventor and scientist.
Johansson invented the gauge block set, also known as "Jo Blocks" ("Johansson gauge blocks"). He was granted his first Swedish patent on 2 May 1901, Swedish patent No. 170 ...
. Johansson was employed in 1888 as an armourer inspector by the
state arsenal Carl Gustafs stads Gevärsfaktori
FFV-Carl Gustaf was a Swedish armaments firm, bought up and merged on several occasions.
History
''Carl Gustafs Stads Gevärsfaktori'' ("Rifle Factory of Carl Gustaf's Town") was founded in 1812 as a state arsenal. The name "Carl Gustaf's To ...
(Rifle Factory of Carl Gustaf's town) in the town of
Eskilstuna, Sweden. He was concerned with the expensive tools for measuring parts for the
Remington rifles then in production under license at Carl Gustaf. When Sweden adopted
a tailored variant of the Mauser carbine in 1894, Johansson was very excited about the chance to study Mauser's methods of measuring, in preparation for production under license at Carl Gustaf (which began several years later). However, a visit to the Mauser factory in
Oberndorf am Neckar
Oberndorf am Neckar (; Swabian: ''Oberndorf am Näggô'') is a town in the district of Rottweil, in Baden-Württemberg, Germany. It is situated on the river Neckar, north of Rottweil. It historically was and currently is a major center of t ...
, Germany, turned out to be a disappointment. On the train home, he thought about the problem, and he came up with the idea of a set of blocks that could be combined to make up any measure.
There had already been a long history of increasing use of gauges up to this time, such as gauges for filing and
go/no go gauge
A go/no-go gauge refers to an inspection tool used to check a workpiece against its allowed tolerances via a go/no-go test. Its name is derived from two tests: the check involves the workpiece having to pass one test (''go'') and fail the other ...
s, which were custom-made individually in a toolroom for use on the shop floor; but there had never been super-precision gauge blocks that could be wrung together to make up different lengths, as Johansson now envisioned.
Back home, Johansson converted his wife's Singer sewing machine to a grinding and lapping machine. He preferred to carry out this precision work at home, as the grinding machines at the rifle factory were not good enough. His wife, Margareta, helped him with the initial prototyping. Once Johansson had demonstrated his set at Carl Gustaf, his employer provided time and resources for him to develop the idea. Johansson was granted his first Swedish patent on 2 May 1901, SE patent No. 17017, called "Gauge Block Sets for Precision Measurement". Johansson formed the Swedish company CE Johansson AB (also known as 'CEJ') on 16 March 1917.
Johansson spent many years in America; during his life he crossed the Atlantic 22 times. The first CEJ gauge block set in America was sold to
Henry M. Leland
Henry Martyn Leland (February 16, 1843 – March 26, 1932) was an American machinist, inventor, engineer and automotive entrepreneur. He founded the two premier American luxury automotive marques, Cadillac and Lincoln.
Early years
Henry M. Lela ...
at the Cadillac Automobile Company around 1908. The first manufacturing plant in America for his gauge block sets was established in
Poughkeepsie, Dutchess County, New York, in 1919. The economic environment of the
post–World War I recession and
depression of 1920–21
Depression may refer to:
Mental health
* Depression (mood), a state of low mood and aversion to activity
* Mood disorders characterized by depression are commonly referred to as simply ''depression'', including:
** Dysthymia, also known as pers ...
did not turn out so well for the company, so in 1923 he wrote a letter to
Henry Ford
Henry Ford (July 30, 1863 – April 7, 1947) was an American industrialist, business magnate, founder of the Ford Motor Company, and chief developer of the assembly line technique of mass production. By creating the first automobile that mi ...
of the
Ford Motor Company
Ford Motor Company (commonly known as Ford) is an American multinational automobile manufacturer headquartered in Dearborn, Michigan, United States. It was founded by Henry Ford and incorporated on June 16, 1903. The company sells automobi ...
, where he proposed a cooperation in order to save his company. Henry Ford became interested, and on 18 November 1923 he began working for Henry Ford in
Dearborn, Michigan
Dearborn is a city in Wayne County in the U.S. state of Michigan. At the 2020 census, it had a population of 109,976. Dearborn is the seventh most-populated city in Michigan and is home to the largest Muslim population in the United States pe ...
. Hounshell (1984), citing Althin (1948) and various archive primary sources, says, "Henry Ford purchased the famous gaugemaking operation of the Swede C. E. Johansson in 1923 and soon moved it into the laboratory facility in Dearborn. Between 1923 and 1927, the Johansson division supplied 'Jo-blocks' to the Ford
toolroom and any manufacturer who could afford them. It also made some of the Ford
'go' and 'no-go' gauges used in production as well as other precision production devices."
[.]
In the early 20th century, the U.S.
inch
Measuring tape with inches
The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelfth") ...
was effectively defined as 25.4000508 mm (with a reference temperature of ) and the U.K. inch at 25.399977 mm (with a reference temperature of ).
When Johansson started manufacturing gauge blocks in inch sizes in 1912, Johansson's compromise was to manufacture gauge blocks with a nominal size of 25.4mm, with a reference temperature of , accurate to within a few parts per million of both official definitions. Because Johansson's blocks were so popular, his blocks became the ''de facto'' standard for manufacturers internationally,
with other manufacturers of gauge blocks following Johansson's definition by producing blocks designed to be equivalent to his.
In 1930, the
British Standards Institution
The British Standards Institution (BSI) is the national standards body of the United Kingdom. BSI produces technical standards on a wide range of products and services and also supplies certification and standards-related services to business ...
adopted an inch of exactly 25.4 mm. The
American Standards Association
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards
Standardization or standardisation is the process of implementing and developing techn ...
followed suit in 1933. By 1935, industry in 16 countries had adopted the "industrial inch" as it came to be known,
effectively endorsing Johansson's pragmatic choice of conversion ratio.
![CEJ co-branding example 001](https://upload.wikimedia.org/wikipedia/commons/f/f2/CEJ_co-branding_example_001.png)
In 1936, at the age of 72, Johansson felt it was time to retire and go back to Sweden. He was awarded the large gold medal of the
Royal Swedish Academy of Engineering Sciences in 1943, shortly after his death.
In 1948
Brown & Sharpe bought the rights to the C.E. Johansson brand from Ford Motor Co.,
and blocks
co-branded
Co-branding is a marketing strategy that involves strategic alliance of multiple brand names jointly used on a single product or service.
Co-branding is an arrangement that associates a single product or service with more than one brand name, o ...
with the C.E. Johansson and
Brown & Sharpe logos were made. Blocks co-branded with the C.E. Johansson and Ford logos are also sometimes still seen in use today.
Gauge pins
Similar to gauge blocks, these are precision-ground cylindrical bars, for use as plug gauges to measure hole diameters, or as parts of
go/no go gauge
A go/no-go gauge refers to an inspection tool used to check a workpiece against its allowed tolerances via a go/no-go test. Its name is derived from two tests: the check involves the workpiece having to pass one test (''go'') and fail the other ...
s or similar applications.
Gauge rollers and balls
These are supplied as sets of individual rollers or balls as used in
roller or ball bearings or
tool and die making applications. Calibration balls can be used to calibrate
contact angle goniometer
A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry derives from two Greek words, Wikt:γωνία, γωνία (''gōnía'') 'angle' and Wikt:μέτρο ...
s,
CNC
Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, grinders, routers and 3D printers) by means of a computer. A CNC machine processes a ...
machines and similar equipment.
See also
*
*
*
Notes
References
* .
*
*
* .
Further reading
*
*
*
External links
The Joy of High TechThe Gauge Block Handbook; US National Institute of Standards & Technology (NIST) Monograph 180 with Corrections; 2004
{{DEFAULTSORT:Gauge Block
Length, distance, or range measuring devices
Metalworking measuring instruments
Swedish inventions