Dial bore gaugeBore gauge / Cylinder gauge

≡Standards, measuring range and accuracy

Standard

JIS B 7515:1982 Cylinder gauges^[1][2]

Measuring range

• General Min 6 mm – max 450 mm (TECLOCK lineup)
• byMaker
  • Mitutoyo CG-AX (511-701–706) 18–35 mm to 250–400 mm
  • Niigata Seiki WCDI-35 18–35 mm (7 interchangeable rods)

^[2][4][3]

Resolution / graduation

• General Determined by the graduation of the indicator (dial indicator) used (e.g. 0.01 mm, 0.001 mm)

^[2][3]

Accuracy (instrument error / maximum permissible error)

• Approach Measured by comparison with a master (ring gauge, micrometer, etc.). JIS B 7515 tests indication accuracy, repeatability, the difference when the contact point is rotated 90° at a time, the effect of the guide plate, measuring force, and so on
• byMaker
  • Mitutoyo CG-AX Repeatability 0.5 µm, measuring force 4–6 N or less

^[2][4]

▦Types

◎Part names and functions

◷How to read the scale

1. The reading is the difference from the reference (the master size set to 0). Add or subtract the difference to or from the master size to get the bore diameter^[3][2][5]
2. The 'turning point' of the pointer when you rock the gauge is the diameter position. In a section containing the hole axis, the indicator points to its maximum when the diameter is at its minimum^[3][7]

✋Usage steps

1. Assembly: loosen the mounting screw, insert the indicator, push it in until the long hand turns 1/10 revolution or more, and fix it^[3]
2. Selecting the rod: choose the rod that suits the size to be measured and adjust the screw-in so that the distance from the contact point tip to the rod tip is about 0.5 mm longer than the target size, then lock it^[3]
3. Cleaning and clamping: wipe the contact point and anvil with a dry cloth and tighten the clamp screw firmly^[6]
4. Zeroing: insert into a ring gauge (setting ring) or micrometer, rock it, and set zero at the point where the indicator reads maximum. Turn the bezel to bring the long hand to 0The diameter in a section perpendicular to the axis (maximum) is found automatically by the guide plate. The diameter in a section containing the axis (minimum) is found by rocking by hand. When setting with an outside micrometer, use the micrometer upright (Mitutoyo)^[3][7][8][6]
5. Insertion: tilt the handle and put the guide plate side in first, then the anvil^[6]
6. Measuring: rock it while watching the scale and read at the point where the indicator shows its maximum (the diameter position). The reading is the difference from the reference ring^[3][7]

!Common measurement mistakes and countermeasures

✓Care, storage, inspection and calibration

Care and storage

• After use, check for damage and clean. If dirt may have got inside, disassemble and clean it, and after drying apply a thin coat of micrometer oil (Mitutoyo)^[6]
• Use the supplied accessories such as interchangeable rods and do not mix them with others. After use, apply rust prevention and put it in the case^[3]
• Do not drop, disassemble or modify (manufacturer's manual)^[3]

Inspection and calibration

• Set zero with a ring gauge, cylindrical master, micrometer, gauge block attachment, bore gauge checker, etc.^[6][7][5][2]
• JIS B 7515 tests include: pushing in 0.1 mm at a time against a reference indicator and plotting an error curve; rocking 3 round trips in a ring gauge and reading the minimum indication, repeated 3 times to find the difference^[2]

The rocking motion and the pointer's turning point suit a diagram (Niigata Seiki manual, Figs. 1–3: diameter a, in a section perpendicular to the axis, is the maximum, found automatically by the guide plate; diameter b, in a section containing the axis, is the minimum, found by rocking by hand).

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