Gauge block

Metric gauge block set

Gauge blocks (also known as gage blocks, Johanssongauges, slip gauges, or Jo blocks) are a system for pro-ducing precision lengths. The individual gauge block isa metal or ceramic block that has been precision groundand lapped to a specific thickness. Gauge blocks come insets of blocks with a range of standard lengths. In use,the blocks are stacked to make up a desired length.An important feature of gauge blocks is that they can bejoined together with very little dimensional uncertainty.The blocks are joined by a sliding process called wring-ing, which causes their ultraflat surfaces to cling together.A small number of gauge blocks can be used to createaccurate lengths within a wide range. By using 3 blocksfrom a set of 30 blocks, one may create any of the 1000lengths from 3.000 to 3.999 mm in 0.001 mm steps (or.3000 to .3999 inches in 0.0001 inch steps). Gauge blockswere invented in 1896 by Swedish machinist Carl EdvardJohansson.[1] They are used as a reference for the calibra-tion of measuring equipment used in machine shops, suchas micrometers, sine bars, calipers, and dial indicators(when used in an inspection role). Gauge blocks are themain means of length standardization used by industry.[1]

1 Description

A gauge block is a block of metal or ceramic with twoopposing faces ground precisely flat and parallel, a pre-cise distance apart. Standard grade blocks are made ofa hardened steel alloy, while calibration grade blocks areoften made of tungsten carbide or chromium carbide be-cause it is harder and wears less.[2] Gauge blocks comein sets of blocks of various lengths, along with two wearblocks, to allow a wide variety of standard lengths to bemade up by stacking them. The length of each block isactually slightly shorter than the nominal length stamped

PLATEN

INTERFEROMETRICLENGTH

WRINGFILM

How gauge blocks are measured.

on it, because the stamped length includes the length ofone wring film, a film of lubricant which separates adja-cent block faces in normal use. This nominal length isknown as the interferometric length.[3]

In use, the blocks are removed from the set, cleanedof their protective coating (petroleum jelly or oil) andwrung together to form a stack of the required dimen-sion, with the minimum number of blocks. Gauge blocksare calibrated to be accurate at 68 °F (20 °C) and shouldbe kept at this temperature when taking measurements.This mitigates the effects of thermal expansion. The wearblocks, made of a harder substance like tungsten carbide,are included at each end of the stack, whenever possible,to protect the gauge blocks from being damaged in use.As a general principle, machinists and toolmakers try touse a stack with the fewest number of blocks, to avoidaccumulation of size errors. For example, a stack totaling.638 that is composed of 2 blocks (a .500 block wrung toa .138 block) is preferable to a stack also totaling .638that is composed of 4 blocks (such as a .200, .149, .151,and .138 all wrung together). However, the stacked erroris still small enough that it is often negligible in all but themost demanding uses. In a busy shop, some of the blockswill be in use elsewhere, so one creates a stack from theblocks available at the time. Typically the few millionthsof an inch difference will not be detectable, or matter, inthe context. Contexts demanding ultimate precision arerarer and more expensive.

1

2 1 DESCRIPTION

1.1 Wringing

36 Johansson gauge blocks wrung together easily support theirown weight.

Wringing is the process of sliding two blocks together sothat their faces lightly bond. Because of their ultraflatsurfaces, when wrung, gauge blocks adhere to each othertightly. Properly wrung blocks may withstand a 75 lbf(330 N) pull.[4] While the exact mechanism that causeswringing is unknown,[4][5] it is believed to be a combina-tion of:[3][4]

• Air pressure applies pressure between the blocks be-cause the air is squeezed out of the joint.

• Surface tension from oil and water vapor that ispresent between the blocks.

• Molecular attraction occurs when two very flat sur-faces are brought into contact. This force causesgauge blocks to adhere even without surface lubri-cants, and in a vacuum.

It is believed that the last two sources are the mostsignificant.[3]

There is no magnetism involved, although to a user theclinging together of the blocks feels a bit like a weak re-frigerator magnet’s clinging to another. Unlike with mag-nets, however, the cling only lasts while the blocks arecompletely joined—the blocks do not attract each otheracross any visible gap, like magnets would.The process of wringing involves four steps:[3]

1. Wiping a clean gauge block across an oiled pad (seethe accessories section).

2. Wiping any extra oil off the gauge block using a drypad (see the accessories section).

3. The block is then slid perpendicularly across theother block while applying moderate pressure untilthey form a cruciform.

4. Finally, the block is rotated until it is inline with theother block.

SLIDE WITHPRESSURE

After use the blocks are re-oiled or greased to protectagainst corrosion. The ability for a given gauge block towring is called wringability; it is officially defined as “theability of two surfaces to adhere tightly to each other inthe absence of external means.” The minimum conditionsfor wringability are a surface finish of 1 microinch (0.025µm) AA or better, and a flatness of at least 5 µin (0.13µm).[3]

There is a formal test to measure wringability. First, theblock is prepared for wringing using the standard pro-cess. The block is then slid across a 2 in (51 mm) ref-erence grade (1 µin (0.025 µm) flatness) quartz opticalflat while applying moderate pressure. Then, the bottomof the gauge block is observed (through the optical flat)for oil or color. For Federal Grades 0.5, 1, and 2 and ISOgrades K, 00, and 0 no oil or color should be visible underthe gauge block. For Federal Grade 3 and ISO grades 1and 2, no more than 20% of the surface area should showoil or color. Note that this test is hard to perform on gaugeblocks thinner than 0.1 in (2.5 mm) because they tend notto be flat in the relaxed state.[3]

SLIDE WITHPRESSURE

OBSERVE COLOR AND PRESENCEOF OIL FROM THE BOTTOM OF FLAT

OPTICAL FLAT

1.2 Accessories

A gauge block accessory set

The pictured accessories provide a set of holders and toolsto extend the usefulness of the gauge block set. They pro-

3

A holder that turns a stack of gauge blocks into an instant, customcaliper or go/no go gauge.

vide a means of securely clamping large stacks together,along with reference points, scribers, and various shapesof blocks that act like caliper jaws, either external or in-ternal. Conical-tip ones ease measurement of center-to-center distances between hole centers. A stack of gaugeblocks with external caliper-jaw accessories, all clampedtogether, acts as a quickly assembled custom-size go orno-go gauge.A gauge block stone is used to remove nicks and burrs tomaintain wringability.[3]

There are two wringing pads used to prepare a gaugeblock for wringing. The first is an oil pad, which appliesa light layer of oil to the block. The second is a dry pad,which removes any excess oil from the block after the oilpad has been used.[3]

2 Grades

Gauge blocks (left in each picture, under optical flats) being usedto measure the height of a ball bearing and a plug gage usinginterferometry.

Gauge blocks are available in various grades, dependingon their intended use.[6] The grading criterion is tightnessof tolerance on their sizes; thus higher grades are madeto tighter tolerances and have higher accuracy and pre-cision. Various grading standards include: JIS B 7506-1997 (Japan)/DIN 861-1980 (Germany), ASME (US),BS 4311: Part 1: 1993 (UK). Tolerances will vary withinthe same grade as the thickness of the material increases.

• reference (AAA): small tolerance (±0.05 μm) usedto establish standards

• calibration (AA): (tolerance +0.10 μm to −0.05 μm)used to calibrate inspection blocks and very highprecision gauging

• inspection (A): (tolerance +0.15 μm to −0.05 μm)used as toolroom standards for setting other gaugingtools

• workshop (B): large tolerance (tolerance +0.25 μmto −0.15 μm) used as shop standards for precisionmeasurement

More recent grade designations include (U.S. FederalSpecification 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

andANSI/ASMEB89.1.9M, which defines both absolutedeviations from nominal dimensions and parallelism lim-its as criteria for grade determination. Generally, gradesare equivalent to former U.S. Federal grades as follows:

• 00— generally equivalent to grade 1 (most exactingflatness and accuracy requirements)

• 0 — generally equivalent to grade 2

• AS-1 — generally equivalent to grade 3 (reportedlystands for American Standard - 1)

• AS-2 — generally less accurate than grade 3

• K — generally equivalent to grade 00 flatness (par-allelism) with grade AS-1 accuracy

The ANSI/ASME standard follows a similar philosophyas set forth in ISO 3650. See the NIST reference be-low for more detailed information on tolerances for eachgrade and block size. Also consult page 2 of: CommercialGauge Block Tolerances (Length refers to the calibratedthickness)

3 Manufacture

Gauge blocks are usually made either from hardened alloytool steels or from cemented carbides (such as tungstencarbide or tantalum carbide). Often the carbide has ahardness of 1500 Vickers hardness. Long series blocksare made from high-quality steel having cross section (35x 9 mm) with holes for clamping two slips together.These

4 6 GAUGE ROLLERS AND BALLS

are also available in carbon steel material. Steel blocksare hardened and tempered. The hardness is importantbecause it slows down the gauge’s rate of wear during use(this is why other kinds of gauges, such as pins, threadplugs, and rings, are also hardened.) The cutting of theblocks to size is accomplished with grinding followed bylapping. Usually no plating or other coating is involved.Blocks are kept very lightly oiled, and are stored and usedin dry climate-controlled conditions; unplated, uncoatedsteel gauge blocks can last for decades without rusting.

4 History

The gauge block set, also known as “Jo Blocks”, wasdeveloped by the Swedish inventor Carl Edvard Johans-son.[7] Johansson was employed in 1888 as an armourerinspector by the state arsenal Carl Gustafs stads Gevärs-faktori [Carl Gustaf Stad’s Rifle Factory] in the town ofEskilstuna, Sweden. He was concerned with the expen-sive tools for measuring parts for the Remington riflesthen in production under license at Carl Gustaf. WhenSweden adopted a tailored variant of the Mauser carbinein 1894, Johansson was very excited about the chanceto study Mauser’s methods of measuring, in preparationfor production under license at Carl Gustaf (which beganseveral years later). However, a visit to the Mauser fac-tory in Oberndorf am Neckar, Germany, turned out to bea disappointment. On the train home, he thought aboutthe problem, and he came up with the idea of a set ofblocks that could be combined to make up any measure.There had already been a long history of increasing useof gauges up to this time, such as gauges for filing andgo/no go gauges, which were custom-made individually ina toolroom for use on the shop floor; but there had neverbeen super-precision gauge blocks that could be wrungtogether to make up different lengths, as Johansson nowenvisioned.Back home, Johansson converted his wife’s Singer sewingmachine to a grinding and lapping machine. He preferredto carry out this precision work at home, as the grindingmachines at the rifle factory were not good enough. Hiswife, Margareta, helped him a lot with the grinding be-sides the household work. Once Johansson had demon-strated his set at Carl Gustaf, his employer provided timeand resources for him to develop the idea. Johansson wasgranted his first Swedish patent on 2May 1901, SE patentNo. 17017, called “Gauge Block Sets for Precision Mea-surement”. Johansson formed the Swedish company CEJohansson AB (also known as 'CEJ') on 16 March 1917.Johansson spent many years in America; during his lifehe crossed the Atlantic 22 times. The first CEJ gaugeblock set in America was sold to Henry M. Leland atthe Cadillac Automobile Company around 1908. Thefirst manufacturing plant in America for his gauge blocksets was established in Poughkeepsie, Dutchess County,

New York, in 1919. The economic environment of thepost–World War I recession and depression of 1920–21did not turn out so well for the company, so in 1923 hewrote a letter to Henry Ford of the FordMotor Company,where he proposed a cooperation in order to save his com-pany. Henry Ford became interested, and on 18 Novem-ber 1923 he began working for Henry Ford in Dearborn,Michigan. Hounshell (1984), citing Althin (1948) andvarious archive primary sources, says, “Henry Ford pur-chased the famous gaugemaking operation of the SwedeC. E. Johansson in 1923 and soon moved it into the lab-oratory facility in Dearborn. Between 1923 and 1927,the Johansson division supplied 'Jo-blocks’ to the Fordtoolroom and any manufacturer who could afford them.It also made some of the Ford 'go' and 'no-go' gaugesused in production as well as other precision productiondevices.”[8]

Co-branding of CEJ, Ford, and B&S logos.

In 1936, at the age of 72, Johansson felt it was time toretire and go back to Sweden. He was awarded the largegold medal of the Royal Swedish Academy of Engineer-ing Sciences in 1943, shortly after his death.At some point the C.E. Johansson brand (or at least itsU.S. presence) became affiliated with Brown & Sharpe,and blocks co-branded with the C.E. Johansson andBrown & Sharpe logos were made. Blocks co-brandedwith the C.E. Johansson and Ford logos are also some-times still seen in use today.

5 Gauge pins

Similar to gauge blocks, these are precision-ground cylin-drical bars, for use as plug gauges to measure hole diame-ters, or as parts of go/no go gauges or similar applications.

6 Gauge rollers and balls

These are supplied as sets of individual rollers or ballsas used in roller or ball bearings or tool and die making

5

applications.

7 References

[1] Doiron, Ted; John Beers (2009), The Gauge Block Hand-book, USA: Dimensional Metrology Group, US NationalInstitute of Standards and Technology, pp. 1–4

[2] Doiron, Ted; John Beers (2009), The Gauge Block Hand-book, USA: Dimensional Metrology Group, US NationalInstitute of Standards and Technology, p. 12

[3] Friedel, Dave, Wringability and Gage Blocks, archivedfrom the original on 2010-12-22, retrieved 2010-12-22.

[4] The Gauge Block Handbook, NIST, p. 138-139

[5] Krar 2005, p. 98.

[6] Hugh Jack: Engineer On a Disk, Grand Valley State Uni-versity, 2001

[7] Althin 1948.

[8] Hounshell 1984, p. 286.

8 Bibliography

• Althin, Torsten K.W. (1948), C.E. Johansson,1864–1943: The Master of Measurement, Stock-holm: Ab. C.E. Johansson [C.E. Johansson corpo-ration], LCCN 74219452.

• Hounshell, David A. (1984), From the AmericanSystem to Mass Production, 1800-1932: The Devel-opment of Manufacturing Technology in the UnitedStates, Baltimore, Maryland: Johns Hopkins Uni-versity Press, ISBN 978-0-8018-2975-8, LCCN83016269

• Krar, Steve F.; Gill, Arthur R.; Smid, Peter (2005),Technology of Machine Tools (6th ed.), McGraw-Hill Career Education, ISBN 978-0-07-723225-2 .

9 Further reading

• Doiron, T. (2007). “20°C—A Short History of theStandard Reference Temperature for Industrial Di-mensional Measurements”. Journal of Research ofthe National Institute of Standards and Technology(National Institute of Science and Technology) 112(1): 1–23. doi:10.6028/jres.112.001.

10 External links• The Joy of High Tech

• The Gauge Block Handbook; US National Instituteof Standards & Technology (NIST) Monograph 180with Corrections; 2004

6 11 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

11 Text and image sources, contributors, and licenses

11.1 Text• Gauge block Source: http://en.wikipedia.org/wiki/Gauge_block?oldid=608931723 Contributors: Dominus, Glenn, Rebrane, Alan Lieft-

ing, Jpgordon, Hooperbloob, Romary, RoySmith, Wtshymanski, Drat, Kevinskogg, Gene Nygaard, GregorB, Rjwilmsi, Graibeard,FayssalF, DerrickOswald, RussBot, Petiatil, SmackBot, Saihtam, Verne Equinox, Chris the speller, Bluebot, Misterbike, Rklawton, Wiz-ard191, Chetvorno, Ale jrb, Oliver dyas, Bodlabo, Thijs!bot, Stephen2810, Saimhe, Yuri r, Glrx, Fcsuper, Spiesr, Sgeureka, VolkovBot,Veddan, Pranay.kondekar, Tomas e, Alexbot, Three-quarter-ten, Addbot, AkhtaBot, Pietrow, Luckas-bot, ArthurBot, Xqbot, Chrisgerman,FrescoBot, Citation bot 1, Bryancpark, Full-date unlinking bot, RjwilmsiBot, ClueBot NG, BZTMPS, Manufacturing unit 9, Chemiekatze,Speedy1910, QuiteWry and Anonymous: 42

11.2 Images• File:CEJ_co-branding_example_001.png Source: http://upload.wikimedia.org/wikipedia/commons/f/f2/CEJ_co-branding_example_

001.png License: CC-BY-SA-3.0 Contributors: Own work Original artist: Manufacturing unit 9• File:Endmaß_Zange.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/05/Endma%C3%9F_Zange.jpg License: CC-BY-

SA-3.0 Contributors: Own work Original artist: Solaris2006• File:GaugeBlockAccessorySet.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/38/GaugeBlockAccessorySet.jpg Li-cense: CC-BY-SA-3.0 Contributors: Own work Original artist: Glenn McKechnie

• File:GaugeBlockMetricSet.jpg Source: http://upload.wikimedia.org/wikipedia/commons/a/ac/GaugeBlockMetricSet.jpg License: CC-BY-SA-3.0 Contributors: Own work Original artist: Glenn McKechnie

• File:Gauge_block_adhesion.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/ed/Gauge_block_adhesion.jpg License:Public domain Contributors: Downloaded 2008-01-12 from <a data-x-rel='nofollow' class='external text' href='http://books.google.com/books?id=YZhKAAAAMAAJ,<span>,&,</span>,pg=PA185'>Clarence Leon Goodrich & Frank Arthur Stanley (1907) Accurate ToolWork, McGraw-Hill, New York, p.185, fig.196</a> on Google Books Original artist: Clarence Leon Goodrich and Frank Arthur Stanley

• File:Gauge_block_interferometric_length.svg Source: http://upload.wikimedia.org/wikipedia/commons/e/e7/Gauge_block_interferometric_length.svg License: CC-BY-SA-3.0 Contributors: Own work Original artist: Wizard191

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• File:Optical_flats_in_use.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5f/Optical_flats_in_use.jpg License: Publicdomain Contributors: Downloaded 2011-03-04 from <a data-x-rel='nofollow' class='external text' href='http://books.google.com/books?id=_-3NAAAAMAAJ,<span>,&,</span>,pg=PA873'>Illustrated World, Vol. 34, No. 5 (January 1921) R.T. Miller, Chicago, USA, p.873</a> on Google Books Original artist: Unknown

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