CaliperVernier caliper / Calliper

≡Standards, measuring range and accuracy

Standard

• JIS B 7507:2022 Geometrical product specifications (GPS) – Dimensional measuring equipment – Calipers (revised based on ISO 13385-1:2019)
• ISO 13385-1:2019 Design and metrological characteristics of callipers
• ASME B89.1.14 Calipers

^[1][2][3][4]Mitutoyo's explanation covers both the terminology change from "instrument error" to "indication error" in JIS B 7507:2016 and the 2022 revision (aligned with ISO 13385-1:2019)

Measuring range

• General 0–150 / 0–200 / 0–300 mm are standard. Long types are 0–1000 mm or more (Mitutoyo M-type goes up to 0–1000 mm, long types up to 2000 mm)
• byMaker
  • Mitutoyo 530 series (M type) 0〜100、0〜150、0〜200、0〜300、0〜600、0〜1000 mm
  • Teclock SSC-650/750/850 (digital) 0〜150、0〜200、0〜300 mm

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Resolution / graduation

• Vernier Minimum reading 0.05 mm (common) or 0.02 mm
• Dial Graduation 0.01 mm or 0.02 mm
• Digital Resolution 0.01 mm
• Vernier construction
  • 0.05 mm: 39 mm of the main scale divided into 20 equal parts (long vernier). Older style: 19 mm divided into 20
  • 0.02 mm: 49 mm of the main scale divided into 50 equal parts
  • With a 0.5 mm main-scale graduation: 12 mm divided into 25 parts (0.02 mm), or 24.5 mm divided into 25 parts (0.02 mm)
• Principle If the length of n vernier divisions is matched to (n−1) main-scale divisions, each division is offset by 1/n. That offset is read at the coincident line

^{[11][12][3][5][7]}

Accuracy (instrument error / maximum permissible error)

• Approach
  • JIS B 7507 (since the 2016 revision) replaced "instrument error" with "indication error" and sets the upper limit with the maximum permissible error (MPE)
  • Error at the outside measuring faces is specified as the "partial surface contact error E"; error at other than the outside measuring faces (inside, depth, step, etc.) is specified separately as the "scale shift error S"
  • ISO 13385-1 (2019) and JIS (2022) made the number and positions of test points specific. For a 150 mm caliper there are at least 5 test points, including points near the maximum and minimum and at both the base and the tip of the jaws
  • E and S are found by clamping a gauge block (or a higher-grade gauge) and subtracting the gauge dimension from the indicated value
• byMaker
  • Mitutoyo 530-101 (M type, 0–150 mm, 0.05 mm) E_MPE ±0.05 mm、S_MPE ±0.07 mm
  • Mitutoyo 530-109 (M type, 0–300 mm) E_MPE ±0.08 mm、S_MPE ±0.10 mm
  • Teclock SSC-650 (digital, 0–150 mm, 0.01 mm) Indication error ±0.02 mm (0–100 mm), ±0.03 mm (100–150 mm)
• Caution The JIS tables are not copied here. Values are manufacturer-published values

^[3][6][9][1]

▦Types

◎Part names and functions

◷How to read the scale

1. Read the main-scale graduation that the vernier zero line points to, in 1 mm unitsExample: zero line between 73 and 74 → 73 mm^[11][5][12]
2. Find the vernier line that aligns exactly with a main-scale line and read its valueExample: with a 0.05 mm vernier, the 0.5 line coincides → 0.50 mm^[11][5][12]
3. Add the two to get the measured valueExample: 73 + 0.50 = 73.50 mm (Niigata Seiki measurement example 2). The sources also give examples of 73.00 / 73.55 / 73.52 mm (0.02 mm vernier)^[11][5][12]
4. Example with a vernier of 19 mm divided into 20 partsExample: zero line between 73 and 74 mm, coinciding line 65 (0.65 mm) → 73.00 + 0.65 = 73.65 mm^[12]
5. Mitutoyo reading example (minimum reading 0.05 mm)Example: main scale 16 mm + vernier 0.15 mm = 16.15 mm^[3]
6. Dial caliper (graduation 0.01 mm)Example: main scale 16 mm + dial 0.13 mm = 16.13 mm^[3]
7. For a 0.02 mm vernier, first get the approximate value from the 0.05 mm side, then read it; this is easier^[11]
8. Judge the coincident line looking straight on (viewing from an angle causes parallax shift)^[5][10][3]

✋Usage steps

1. Preparation: wipe the measuring faces, the beam's sliding surface, and the scale face to remove chips and dirtWipe the sliding surface (reference surface) with a small amount of micrometer oil (Mitutoyo). Niigata Seiki says to apply clean oil to the sliding surface^[11][5][10]
2. Operation check: move the slider through its full range and check for sticking, uneven movement, and play up and down^[5][10]
3. Gap check: close the outside measuring faces and hold them up to the light; check that no light leaks through (or that only a uniform faint light shows). A little light at the inside measuring faces is normal^[11][5][10]
4. Zero check: close the outside measuring faces and check that the zero lines of the beam and vernier align. On digital types, reset the origin with ORIGIN after changing the battery^{[11][5][10][3]}
5. Outside measurement: gently clamp the workpiece with the outside jaws, bring them into contact with proper, even force, and read while still clampedKeep the workpiece's center line perpendicular to the jaws, and clamp the workpiece as close to the beam (the base of the jaws) as possible^[5][12][10]
6. Inside measurement: insert the inside jaws as deep as possible and seat the measuring faces. For a hole, read where the reading is at its maximum; for a groove width, read where it is at its minimumMake the line joining the jaw measuring faces coincide with the hole diameter and parallel to the hole's center line^[5][3][12]
7. Step measurement: put the beam-side step measuring face against the workpiece and move the slider until the slider-side step measuring face meets the step surface, then readBring the entire step measuring face into contact with the workpiece. Mitutoyo does not recommend measuring a step with the depth bar, because the contact area is small and the posture is unstable^[5]
8. Depth measurement: put the depth measuring face at the end of the beam against the top surface of the workpiece and move the slider until the depth bar touches the bottom, then readThe caliper's depth measuring face is narrow and unstable, so place it square to the workpiece; do not tilt it. Facing the relieved side of the depth bar tip toward the workpiece lets you measure correctly even with a corner radius (R). Read the minimum value for depth. Mitutoyo introduces a depth base attachment (optional)^[5][12][3]
9. Recording: record the value as read. Digital types can use data output^[8]

!Common measurement mistakes and countermeasures

✓Care, storage, inspection and calibration

Care and storage

• After use, wipe off moisture, oil, and dirt, and store with a thin coat of rust-preventive oil (wipe waterproof types too)^[5][3][10]
• For storage, open the outside jaws about 0.2–2 mm and keep the locking screw loosened. Do not store fully closed^[10][3]
• Avoid direct sunlight, high or low temperature, high humidity, and places with much dust or oil mist^[5][3][10]
• Do not drop or bump it. The jaws are sharp, so handle with care^[11][3]
• Remove the battery from digital types if not used for 3 months or more. Do not engrave the scale with an electric pen^[3][10]
• If used where water-soluble cutting fluid splashes, always apply rust prevention after cleaning^[10]

Inspection and calibration

• Daily check: check the gap (light) at the outside measuring faces and the zero point every time^[11][5][10]
• Periodic inspection: clamp gauge blocks (or a higher-grade gauge) and subtract the gauge dimension from the indicated value to find the partial surface contact error E. For inside, depth, and step, build up gauges to find the scale shift error S^[3]
• ISO 13385-1:2019 / JIS B 7507:2022 require testing 90 % or more of the measuring range, and testing the base and tip of the jaws near the maximum and minimum. A 150 mm caliper has at least 5 test points^[3]
• The reference standard should preferably be known to an accuracy at least 10 times finer than the smallest graduation of the instrument under test (e.g., for a caliper graduated at 0.001 inch, a standard known to 0.0001 inch)^[8]
• A calibration certificate states the instrument identification, the standard and temperature used, traceability, measured values and permissible error, uncertainty, and pass/fail^[8]

A caliper's structure does not follow the Abbe principle (the scale axis and the measuring point are not in a straight line). This is useful for explaining the accuracy difference from a micrometer. Mitutoyo explains that the name "Nogisu" (the Japanese word for caliper) comes from Nonius, who is said to have devised the vernier.

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