Blog of Adamant Namiki Precision Jewel Co., Ltd.

Bore Measuring Equipment

Features and measurement principles of the measuring devices for inner diameter, roundness and cylindricity, 3D shapes, surface roughness, and visual defects
   Last Modified:    Published: 2021/12

There are two methods for measuring the inner diameter of a hole: contact type and non-contact type.
Traditionally, measurements have been taken using contact-type products, such as pin gauges, caliper gauges, hole tests, and contact-type displacement sensors.
With this method, the guage head comes into contact with the inside of the hole. This may cause damage, so it is not suitable for measuring parts that require high-precision machining.

Optical probe
1. Broadband light (near infrared)
2. Light reflected by the inner circumferential surface of the workpiece / Light reflected by the reference surface
3. Optical and control unit
4. Computing and analysis
Interference light: Light interference occurs due to differences in optical path lengths
Scanning mirror: Rotated by motor
Reference quartz pipe: Fixed
Spectrometer / Diffraction grating

Non-contact methods of measurement use devices such as optical measuring microscopes or projectors to measure inside the hole.
These devices can only measure the inner edge of the hole, so they are not suitable for taking measurements deeping inside.
Instead, they are used for measuring holes drilled in thin objects, and for checking the shape of the ends of the hole.
For non-contact type measuring inside of the hole, air microsensors can be used.
With these, a stylus with a nozzle is inserted into the hole and the inner diameter measured based on changes in pressure.
Measurements such as mean bore diameter require multiple nozzles.
Optical sensors, such as laser displacement meters and optical interferometers, can be used for more accurate and stable measurement of inner diameter.
A probe to which the sensor is attached is inserted into the hole, and measuring is performed by rotating either the probe or the object itself.
By using an optical sensor, it is possible to take a wide range of measurements, including minimum/maximum inner diameter, and internal shape.

Adamant Namiki's optical inner wall precision measuring system negates the need for separate measurements on dedicated equipment. Our device is capable of non-contact, simultaneous measurement of inner diameter, roundness, roughness, and shape. Click here for more info.

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