Gauge blockGauge block (gage block)

≡Standards, measuring range and accuracy

Standard

• JIS B 7506:2004 Gauge blocks (revised on the basis of ISO 3650:1998)
• ISO 3650:1998 Length standards — Gauge blocks (grades K, 0, 1, 2)
• ASME B89.1.9 Gage Blocks (grades K, 00, 0, AS-1, AS-2)

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Measuring range

• General Nominal size 0.5–1000 mm
• Set example 1 mm base sets, etc. (Mitutoyo)

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Resolution / graduation

• Description A reference with no graduations. The dimension is defined by the tolerances of each grade (tolerance on length and tolerance on variation in length)

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Accuracy (instrument error / maximum permissible error)

• Grade ISO 3650 has calibration grade K and grades 0, 1, 2. ASME B89.1.9 has K, 00, 0, AS-1, AS-2
• Approach Each grade sets a 'tolerance on length at any point (±te)' and a 'tolerance on variation in length (tv)' (do not copy the tables as is)
• Typical use The public sources checked do not state which use applies to each grade (unverified)
• byMaker

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▦Types

◎Part names and functions

◷How to read the scale

1. Choosing a combination: use as few blocks as possible and the thickest ones possible, deciding the dimension from the smallest digitExample: 23.456 mm = 1.006 + 1.45 + 21 (Mitutoyo's example). 25.435 mm = 1.005 + 1.03 + 1.4 + 22^[9][8]

✋Usage steps

1. Environment: use in a thermally stable place. If the temperature differs greatly from 20 °C and the workpiece and blocks have different expansion coefficients, correct for it^[7][10]
2. Cleaning: clean the measuring faces of the blocks to be used with cleaning fluid and cleaning paper^[9][7][8]
3. Burr check: gently place an optical flat on the measuring face, slide it lightly and see whether interference fringes appear, and whether they vanish when pressed lightlyNo fringes visible → large burr or dirt. Fringes vanish when pressed → no burr. Fringes remain locally → burr present. Fringes move together with the flat when it is moved → burr on the flat^[9][8][7]
4. Deburring: wipe the block and the stone (Ceraston or Arkansas stone) with solvent, lay the burred face on the stone and move it back and forth about 10 times with light force. Press thin blocks evenly with a piece of rubber. If the burr will not come off, replace the block^[9][8][7]
5. Oil film: spread a very small amount of oil (grease, spindle oil, petroleum jelly, etc.) on the measuring face and wipe it off until almost none remains. Too little oil makes wringing difficult and speeds up wear^[9][8][7][5]
6. Wringing: for thick blocks, cross them at 90° at the center of the measuring faces, lay them together, and rotate them with light pressure until they join^[9][8]
7. Thick and thin: lay one side of the thin block on the thick block and slide it, pressing the whole overlap, until they join^[9][8]
8. Thin to thin: to prevent bending, first wring a thin block to a thick block, wring the other thin block onto it, and finally remove the thick block. Check the wringing with an optical flat^[9][8]
9. After assembly, wipe the exposed measuring faces and stack up in the same way^[8]

!Common measurement mistakes and countermeasures

✓Care, storage, inspection and calibration

Care and storage

• After use, check for damage; after cleaning, rust-proof steel blocks with a cloth soaked in rust-preventive oil^[7]
• Store away from high temperature and humidity, dust and oil mist^[7]
• Ceramic has about 10 times the wear resistance of steel, resists rust, and has a thermal expansion coefficient close to steel (Mitutoyo US material)^[6]

Inspection and calibration

• Gauge blocks themselves are calibrated by light-wave interferometer or by comparison measurement (a table-of-contents item in JIS B 7506)^[2]
• Wringing test: put it against an optical flat and view from behind. Grades K, 00 and 0 must show no color or oil; grades AS-1 and AS-2 must be 80% or more colorless (ASME grades, Starrett)^[5]
• Gauge blocks are used as the reference for calibrating calipers, micrometers, height gauges, etc. Traceability leads to national standards^[6][8]

A reference that realizes in industry the definition of the metre (1983: the length light travels in vacuum in 1/299 792 458 s) (Mitutoyo). The official JIS name is 'block gauge', while manufacturers more often say 'gauge block'.

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