page 164

Long Island Indicator Service Inc

Swiss Precision Tool Repairs, Sales & Spare Parts







Gage blocks - Gauge blocks
Certified gage blocks for calibration of micrometers, indicators, calipers etc.


Each rectangular steel or ceramic gage block comes with a serial number engraved and a certificate of accuracy traceable to NIST. These have a tolerance grade ASME 0, ideally suited for shop calibration as well as the inspection room.

They can be wrung together to create a larger span, 6" for calibrating a caliper, for instance. In fact, you can take any combination of blocks and put them end-to-end to create your desired length. For example, combining a 25 mm block with a 30 mm block will result in the equivalent of a 55 mm block.

A word of warning: it can be very tricky to handle more than two blocks at a time, so think carefully about which blocks you need to buy.

For ISO purposes, keep track of these serial numbers and keep a copy of the certificate with your calibration records. When you calibrate your instrument make note of the instrument's serial number and the serial numbers of the gage blocks which you used to calibrate it. Additionally, have the gage blocks certified by a local calibration lab on an annual basis and then keep the current certificate of calibration with your records.

These gage blocks are ideal for any micrometer or dial indicator having up to .0001" discrimination. If you don't need that kind of accuracy, consider getting a complete gage block set shown further down this page.

Instead of buying individual blocks for micrometer calibration you may want to look at the Micrometer Calibration Set on page 7.

1" rectangular steel gage block shown with an Etalon indicating micrometer

High quality rectangular steel gauge blocks - NIST certified - ASME 0

Dimension (steel)


Order number

2017 Price




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42.85 order now

.0625" (1/16")



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29.25 order now




29.25 order now




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±.000003" (*)


83.95 order now




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243.00 order now




287.00 order now

longer than 4"

measuring rod may be more suitable (and it's cheaper). See page 58


Calibration certificate is included. All gage blocks are calibrated by the factory to NIST or International Standards on the date of manufacture. Your certificates will not have current dating. If you require current dating, you will have to send these gage blocks to a calibration laboratory. Please read further information below.

All gage blocks above have these uniform dimensions:

  • width = .354"
  • height = 1.181"

Gage block source: these high quality blocks are produced by Mitotoyo of Japan.

(*) high accuracy 1" block is ASME grade 00

† The .005" block is well suited for calibration of paper and film thickness gages. It will be necessary to handle this gage block with extreme care because of its thickness (or lack thereof).


High quality rectangular metric ceramic gauge blocks - NIST certified - ASME 0


Except where noted, these Grade 0 metric gage blocks are high quality ceramic. Why aren't they all made of ceramic? Because some sizes are too small and ceramic would be too brittle; some sizes are too large and the gage block would be too expensive.


You will have no trouble combining ceramic with steel blocks. For example, you can safely combine a 0.5 mm steel block with the 1 mm ceramic block to achieve the equivalent of a 1.5 mm block. They are fully compatible. The smallest metric gage block available is 0.1 mm (steel only).

Take a closer look at some of the reasons to go ceramic:

  • Corrosion resistant (it's okay to handle these with your bare hands)
  • No burrs because it will not scratch. If dented, any resulting burrs can be removed with a ceramic stone
  • Abrasion resistance is 10 times that of steel gage blocks
  • Will not change dimension over time
  • Black printing makes it easy to see the dimensions of these blocks
  • Non magnetic which means it won't attract metal chips
  • High wringing force due to the density of the ceramic
  • Much harder than steel (1350 HV)
  • Thermal expansion coefficient is quite similar to that of steel so they can safely be combined
  • CERA is one of the toughest ceramics available and is extremely difficult to crack under normal use.



CERA blocks are available as a complete set or as individual pieces. The 112 block set is shown.

Rectangular Ceramic

ASME Grade 0

Mitutoyo Part Number

2017 Price in US$

47 piece ceramic set

1 mm to 100 mm


check stock and price

0.1 mm (steel)

±0.00012 mm



0.2 mm (steel)

±0.00012 mm



0.5 mm

±0.00012 mm


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1 mm

±0.00012 mm


1.005 mm

±0.00012 mm


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2 mm

±0.00012 mm


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2.5 mm

±0.00012 mm



3 mm

±0.00012 mm


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4 mm

±0.00012 mm



5 mm

±0.00012 mm


6 mm

±0.00012 mm


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7 mm

±0.00012 mm


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8 mm

±0.00012 mm


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9 mm

±0.00012 mm


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10 mm

±0.00012 mm



15 mm

±0.00014 mm



20 mm

±0.00014 mm



25 mm

±0.00014 mm


check stock and price

30 mm

±0.00020 mm



50 mm

±0.00020 mm


check stock and price

100 mm

±0.00030 mm


check stock and price


Calibration certificate is included. All gage blocks are calibrated by the factory to NIST or International Standards on the date of manufacture. All blocks can be combined to create larger dimensions. Please read further information below.

High quality inch ceramic rectangular gage blocks - NIST certified


Whether ceramic or steel, both serve the same function. Ceramic doesn't expand as much as steel does, so the blocks are accurate over a wider temperature range. Ceramic (CERA) blocks have the added advantage of never getting rusty (cleaning is easier) and of resisting scratches (which can ruin a gauge block in short order). You can handle these without any special precautions since fingerprints won't affect the blocks. Also, the size may be easier to read because it's printed in black on a white surface. These are inspection grade blocks which conform to ASME Grade 0.

For more information on ceramic blocks, take a look at the section directly above.

If you don't have a preference, we'd suggest getting the ceramic CERA block. Even though they may cost more, they're also hassle-free. NIST certificate included. Furthermore, you can easily combine the steel and the CERA blocks. They will "wring" together with no trouble. Very small sizes will not be available in ceramic and you will have to resort to steel in those cases.



±0.000006 inch




±0.000005 inch




±0.000005 inch




±0.000006 inch


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±0.000006 inch




±0.000006 inch


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±0.000006 inch


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* while supply lasts

Product description as provided by the manufacturer:

The Mitutoyo grade 0 rectangular gage block is made of ceramic, has its nominal length engraved in inches, and is supplied with a Mitutoyo inspection certificate that states that the block meets American Society of Mechanical Engineers (ASME) B89.1.9-2002 grade standard for flatness, length, parallelism, and surface finish. The inspection certificate specifies the deviation of the individual block from its nominal length. Gage blocks are commonly used to calibrate fixtures and precision instruments in workshop, inspection, and dimensional metrology applications, to inspect tools such as mounting tools, cutters, fixtures, and mechanical parts, and in the gage manufacturing process itself.

This grade 0 gage block is commonly used in workshop and inspection applications to calibrate and inspect mechanical parts and tools, to verify the accuracy of plug and snap gages, and to set electronic measuring devices. It is made of ceramic which resists corrosion, abrasion, and burrs, withstands high temperatures without melting (high thermal expansion resistance), and provides dimensional stability. This gage block has a rectangular base for accurate wringing. Nominal length is measured in inches, and is indicated on the block with laser-etched, black characters. The length of a gage block is usually slightly shorter than its stamped nominal length, to account for the thin layer of oil or wring film used when two or more blocks are wrung together. An identification number is laser-etched on the block for traceability. The block has a depth of 0.355 inches. It comes in a carrying case with a padded, formed interior.

This gage block is supplied with a Mitutoyo inspection certificate [National Institute of Standards in Engineering (NIST)-traceable] that the block meets ASME B89.1.9-2002 standard for flatness, length, parallelism, and surface finish.

Gage blocks (also called gauge blocks, Hoke blocks, Jo blocks, slip gages, and Johansson gages) are blocks used to calibrate measuring equipment and to standardize the measurement of length in manufacturing industries. They are commonly made of precision-ground steel, ceramic, or carbide material, and have a square or rectangular base. Each block has a unique identification number. Length is in inch or millimeter measurement. They can be sold individually, and are also sold in sets with blocks of varying lengths. Gage blocks can be wrung together to create a required length. Wringing is the process of lapping blocks together with a small amount of oil. They are standardized by grade, which refers to the tolerance or deviation of an individual block from its nominal length. Gage block grades are defined for flatness, length, parallelism, and surface finish. Some grades of gage blocks meet standards such as ASME, Association for Iron and Steel (AIST), and International Organization for Standards (ISO). Application and required level of accuracy dictate which grade of gage block should be used. Some manufacturers provide an internally-generated certificate of inspection to verify that a gage block meets grade standards. Gage blocks can also go through a calibration certification process to verify measurement accuracy. Calibration is performed by an accredited facility. Gage blocks are commonly recalibrated after use to ensure dimensional accuracy. If a gage block does not meet calibration standards, it should no longer be used. Both a certificate of inspection and a calibration certificate specify the deviation from the nominal length.

What is the difference between the various grades?


The gauge blocks offered above have tolerances which have the broadest range of use suitable for the inspection room as well as for shop set-ups. The tolerances which we show are the deviation of length at any point from nominal length. For a 1-inch gage block with ±.000006" tolerance, this means that at any point the gauge block may be as long as 1.000006" or as short as .999994". For all practical purposes, this is as close to 1" as you're likely to want to get.

Let us take a 1-inch gage block as an example. The length deviation at any point, from the nominal length is as follows:

  • ASME Grade 00: ± 3 µin
  • ASME Grade 0: ± 6 µin
  • ASME Grade AS-1: ± 12 µin
  • ASME Grade AS-2: ± 24 µin

Calibration Grade 00: These higher accuracy gage blocks are indended for use within a controlled environment by skilled inspection staff. They are mainly used as reference standards for setting high precision measuring equipment and for the calibration of lower grade gage blocks. They are not intended for shop use.

Inspection Grade 0: This grade is used within an inspection area to verify the accurcy of plug and snap gages as well as for the setting of electronic measuring devices.

Workshop Grade AS-1: These gage blocks are intended for shop floor use to set and calibrate fixtures as well as precision instruments such as calipers, indicators and micrometers.


B&S metric gage block set - carbide


Brown & Sharpe tungsten carbide deluxe 112 piece metric gage block set meets or exceeds Federal specification GGG-G-15c. These blocks are Grade 2 (A+) suitable as working standards in inspection rooms to set and calibrate measuring instruments and other equipment. Every block is certified, with serial number, and each set includes a certificate of calibration and traceability. Housed in a sturdy and well laid-out wooden box.

This is not one of those cheap Chinese imports (which we do not sell on principle), but the highest quality gage block set designed for professional use.

This deluxe 112 piece set includes the following blocks:

0.5 mm, 1.00 mm, 1.0005 mm, 1.001 mm through 1.009 mm, 1.01 through 1.49 mm, 1.5 through 24.5 mm, 25 mm, 50 mm, 75 mm and 100 mm.

  • Deluxe 112 piece tungsten carbide, rectangular metric gage block set #43009 ... inquire

Please allow 2-3 weeks for delivery. Calibration will have been made at time of manufacture and may not have a current date. This does not affect the validity of the certificate. Please read section below.


Calibration certificate included


You will receive a certificate which is NIST traceable. But, take note: gage blocks are calibrated by the factory on the date of manufacture. Thus, the gage blocks you receive may have calibration dates many months old.

Your certificate will be valid for one year after you put the gage blocks into service. For instance: the gage block is factory certified in January 2011 and you place the gage block into service on August 2014. You should then create a calibration cycle wherein the gage block will need re-certification on August 2015, one year later, unless your quality manager has established a different length calibration cycle.

On rare occasions, a customer may need date-current certificates. You must place a request for them. It will involve 3-4 weeks of delivery time and there will be a charge for this calibration. It may be to your advantage to have them calibrated at a local lab. This will certainly save you time and money.

If your customer, or your quality manual has different requirements, then disregard all of this information and follow your customer's or manual's instructions.

Mitutoyo 182-302, 6"/150mm Semi-Flexible Rule, (1/16, 1/32, 1/64", 1mm, 0.5mm), 5/8" Wide, Satin Chrome, Engraved Front Side Only


How do I take care of my blocks?


Handle these with kid gloves. No kidding. They're your length masters and have to maintain their pristine condition in order to remain reliable. Scratches, dents and dings will all alter the dimension of your block rendering its usefulness questionable.

Use an optical flat from time to time to check the gage block's flatness (see page 7 for a relatively inexpensive set). Scratches or dents will show up as distortions in the light bands of the optical flat (you may want to research how optical flats work, if you're not yet familiar). At this point you can use a gage block stone (sometimes called "Arkansas Stone" or Ceraston) to gently remove any burrs or high spots caused by the scratches. The procedure requires some skill and practice and may be best left to someone who's familiar with the process.

How-To: Lay the stone on the table and slide the gage block along the stone surface - not the other way around! Done correctly, you won't be changing the gage block's dimensions, but you will get rid of the burrs.

Steel blocks can get rusty, so coat them with a bit of oil whenever they're being stored. Then clean the oil off before using them. At this point, don't touch the bare metal with your hands. Pros use a pair of tongs, but we'd suggest you leave this to the pros. You'll probably only prove that you're all thumbs and consequently drop the gage block. Instead, use some lint-free tissue paper or clean cloth to pick up and maneuver the blocks.

If you get finger prints on them, clean with alcohol and then coat with good, clean oil. For long term storage, a bit of Vaseline works well. Put the blocks in a labeled, clean plastic bag and in a safe, sturdy container when you're done. You don't want the blocks to bang against each other. If any block isn't shiny, smooth and scratch free, have it examined and certified by a gage lab.

Ceramic gage blocks have fewer issues. No need to worry about finger prints, or rust. You should still treat them with respect, since they're quite costly to replace.

Mitutoyo 516-650E Maintenance Kit for Gage Blocks contains the following items:

  • a ceraston (or Arkansas stone) (601645) for removing burrs
  • an optical flat (600003) for checking for burrs
  • tweezers (600004) for handling small gage blocks
  • a blower brush (600005) for blowing dust off the measuring surface
  • cleaning paper (600006) for removing oil and dirt
  • an artificial leather mat (600007) for placing under gage blocks
  • a 100 mL reagent bottle, and cloth gloves for handling blocks.
  • all items are contained within a portable wooden case
  • Mitutoyo 516-650E Maintenance Kit … check price and stock

If you're a neat freak, or otherwise retentive, working with gauge blocks should be right up your alley. Pull on those cotton gloves and enjoy!

Gage vs. Gauge


In American manufacturing circles, gage is the preferred spelling.

When we first incorporated our business we had to give our attorney a number of alternate business names and one of them included the word gage. He took an irate stance and with his pen in hand jabbed at the dictionary page where gauge was given in definition. "No!" we insisted, "machinists and manufacturers beg to differ." Even such a venerable American manufacturer as Federal Gage uses this spelling. He shook his head in disbelief so we thought it best to avoid the word altogether.

Because many people from different disciplines google for gauge, we thought it wise to include both spellings on the same page. We've also rather arbitrarily decided that gage would suit the inch product and gauge would be linked to the metric.


As long as we don't misspell it, and that happens easily. Guage is not a word in the English language... yet. Here's a cute story told us by a generous friend of Long Island Indicator and we hope he won't mind us retelling it here:

One of our teams made a poster with stick-on letters summarizing their goals. One goal referred to "Guages." I took my razor and carefully began peeling off the letters U and A so that I could switch them on the poster.

As I was doing so, one team member indignantly informed me, "You know, that is an alternate spelling of gage."

I replied, "Actually, G-A-U-G-E is an alternate spelling of gage. What you have here is G-U-A-G-E which spells 'goo-wahj' which I guess would be where Elmer Fudd parks his car."

(with thanks to Lemar Luke of Mechanical Calibration Laboratory, Ogden UT)

Footnote of interest: Lee Hawkins, Observatory Engineer at Appalachian State University tells us that—in his field—gauges measure an environmental effect such as a pressure gauge or force gauge, whereas "gage is reserved for an instrument which measures a dimension of some sort."


Some Questions and Answers about gage blocks


Q: Can you guys by any chance calibrate these after my one year period has expired?  The reason why I am asking this is because the people that we usually have calibrate our equipment and stuff want to charge me almost $500 to calibrate these blocks (which is way more than buying a brand new set). And since we are ISO certified, I have to have this type of stuff calibrated on a regular basis.

A: This is the dilemma exactly. The best you can hope for is to shop around and see if you can find a gage lab that's less expensive. Calibrating a set often costs more than buying a new inexpensive set. The lesson to learn here is, if annual calibration is required, throw the old set out and buy a new one. Weird but true… To answer your question, we can not calibrate gage blocks. We are not equipped to do that.






BesTest and TesaTast Indicator Repair Manual … page 177
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Compac Test Indicator Repair Manual … page 194
Mitutoyo Test Indicator Repair Manual … page 102

Long Island Indicator Service Inc
14 Sarah Drive — Hauppauge NY 11788 — USA

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This page's most recent revision: 24 MAY 2017
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Original photographs and content copyright 2017 by JWGrum


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