日本語

Angles and flatness

Surface plateSurface plate

Also called: stone surface plate, granite surface plate, cast iron surface plate, Graplate (Mitutoyo product name)

Illustration of using a surface plate

≡Standards, measuring range and accuracy

Standard
  • JIS B 7513:1992 Precision surface plates
  • ISO 8512-1:1990 (cast iron)
  • ISO 8512-2:1990 (granite)
[1][2][3]
Measuring range
  • byMaker
    • Obishi Keiki stone precision surface plate 300×300 mm to 1500×1000 mm and larger
[6][4]1 source, for reference
Resolution / graduation
—Not confirmed in public sourcesA reference with no graduations
Accuracy (instrument error / maximum permissible error)
  • Grade Grades 00, 0 and 1 (Obishi Keiki stone surface plates). ISO 8512 has grades 0, 1, 2, 3
  • byMaker
    • Obishi Keiki 300×300 mm Flatness: grade 00 2.0 µm, grade 0 4.0 µm, grade 1 8 µm
[6][2]

▦Types

Stone (gabbro, granite, etc.)

Hard, wear resistant, little change over time, and does not rust (Obishi Keiki). More than twice the hardness of cast iron (Mitutoyo)[4][5]

Cast iron

[2]1 source, for reference

◎Part names and functions

#NameEnglishFunction
1Plate body (working surface) / support points (3) / auxiliary support points / adjusting bolts / lock nuts / standPlate, supports, levelling bolts, standSupported at 3 points to level it.[4]

✋Usage steps

  1. Installation: place it level on a stable stand with 3-point support (two points on the left, one on the right). Use the 2 auxiliary support points to prevent tipping[4]
  2. Leveling: loosen the lock nuts, retract the auxiliary support points so it rests on 3 points, place the level at the center of the left support point and then at the center of the plate, and level it with the adjusting bolts. Repeat this, tighten the lock nuts, and check again[4]
  3. For high-accuracy inspection, place it on a concrete base isolated from its surroundings, or on a sturdy stand on an isolated floor[4]
  4. Before use, clean the working surface and the workpiece and let them settle to the same temperature[4][7]
  5. Do not always use the same spot on the working surface; use the whole surface evenly[4]

Printed from Kezuriba (kezuriba.net/en/gauges/surface-plate/)

!Common measurement mistakes and countermeasures

Placing it where vibration or temperature change is large

Why

CountermeasureAvoid[4]

Excessive load or impact

Why

CountermeasureAvoid[4]

✓Care, storage, inspection and calibration

Care and storage

Inspection and calibration

⇄Related instruments

Height gaugeV-blockPrecision levelLever-type dial indicator (dial test indicator)

📚Sources

Content without a mark is what agreed across two or more sources from different publishers. Procedures and cautions are summarized in Kezuriba's own words based on the sources, and the diagrams were drawn by Kezuriba. Accuracy values are manufacturers' published figures, not values from JIS tables.

  1. Japanese Standards Association (JSA), "JIS B 7513:1992 Precision surface plates (bibliographic record)"
  2. ISO「ISO 8512-1:1990 Surface plates — Part 1: Cast iron」
  3. ISO「ISO 8512-2:1990 Surface plates — Part 2: Granite」
  4. Obishi Keiki, "Stone Precision Surface Plate Instruction Manual BA201"
  5. Mitutoyo, "Precision Granite Surface Plate (Graplate) Product Page"
  6. Obishi Keiki, "Stone Precision Surface Plate Product Page"
  7. Mitutoyo, "Check Points for Measuring Instruments (Catalog No. E12024)"
  8. Obishi Keiki, "How to Measure Straightness with a Level"