In the measurement and control category, this article’s topic will be inspection equipment — an introduction to inspection equipment, its types, and what’s needed for its maintenance and care. We’ll get to know gauges and the types of gauges.
Making parts to the desired dimensions and specifications gains its value through the development of the measurement and control system. It’s not possible for every part to be made to exactly the same dimension and quality. However, the operator can be required to make the assigned part within two previously accepted dimensional limits and the desired quality. To reach this, the operator must be given the necessary measuring and inspection tools, and must be able to use these tools well.
Inspection Equipment and Its Types
The tool used in the measurement and inspection carried out at any stage of manufacturing or assembly, to check whether the resulting product or the semi-finished part coming from the manufacturer has the specified characteristics, is called inspection equipment.
We can roughly group inspection equipment into 4 categories.
- Fixtures/Comparators
- Reference standards (etalons)
- Gauges
- Instruments
Fixtures/Comparators
This is inspection equipment that checks, by comparison against a working reference standard or directly, whether the product obtained at any stage of manufacturing is within the specified dimensional limits.
Types of comparators:
1-) mechanical inspection comparators.
2-) electronic inspection comparators.
3-) pneumatic inspection comparators
4-) air-gauging (Solex-type) comparators
Reference Standard (Etalon)
Inspection equipment that has been precisely machined according to drawing values and whose actual value has been metrologically measured and determined, used to zero a comparator before starting measurement, is called a “reference standard” (etalon).
Zeroing measuring instruments with reference standard equipment is done at an ambient temperature of 20°C. Differences in thermal expansion of the reference-standard tools at different ambient temperatures can lead to misleading results.
What is calibration (étalonnage)?
Calibration is the complete set of operations based on determining the errors of a measuring instrument according to national or international references.
Why is calibration performed?
The purpose of calibration: Calibration is a mandatory procedure. It must be done periodically. Because it allows changes occurring in a measuring instrument to be tracked. It prevents disagreements over measurements, and therefore prevents “scrapped parts.”
Gauges
Gauges are equipment used to check, in series, whether the product obtained at any stage of manufacturing is within the specified dimensional limits.
Snap gauges (go/no-go gauges) are inspection equipment used to check the outside diameter of shafts. One side of this gauge passes over the shaft — the other side doesn’t. If this is the case, the machined dimension is understood to be within the tolerance limits. If both sides pass, the machined dimension is smaller than the tolerance limits. If neither side passes, the machined dimension is understood to be larger than the tolerance limits.
25 J6 snap gauge (picture above)
Plug gauges: are inspection equipment used for hole diameters or internal dimensions. This type of gauge can give inaccurate results if the hole is out-of-round (oval).
There are also single-ended plug gauges. On this type of gauge, the go and no-go sections are on the same side. (above)
Another go/no-go gauge used for checking internal diameters, known as a Go/No-Go gauge. (above)
thread gauges: an internal thread gauge for checking screws and nuts (picture above)
Johansson gauge blocks, meanwhile, are generally flawlessly machined blocks used for checking measuring instruments such as calipers and micrometers (above). For detailed information, see: Johansson Gauge Blocks and Their Use
Instruments
This is equipment used to determine, with a known uncertainty, whether the actual value obtained at any stage of manufacturing or on the finished product is within the dimensions and tolerances specified in the manufacturing drawing. For example, 3D (coordinate measuring machines), digital height gauges, gear tooth measuring instruments, calipers, micrometers, surface roughness testers, etc.
How Is the Protection and Continued Reliability of Inspection Equipment Ensured
- Attention must be paid to keeping inspection equipment clean.
- Inspection equipment should not be dropped on the floor.
- Inspection equipment should be protected against impacts and shocks.
- For tools that require operating instructions, the instructions must always be requested, and training should be obtained if needed.
- In case of malfunction, the tool should not be tampered with; the relevant department should be notified immediately.
- Inspection tools should not be used for purposes other than their intended one.
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