The difference between internal thread addendum gages and other gauges is first reflected in the targeted detection object. This type of gauge is specially used for the size detection of the internal thread crest part, focusing on the key parameters such as the profile and height of the internal thread crest, while other gauges often have different detection targets. For example, ordinary plug gauges are mainly used to detect the diameter size of holes, and ring gauges measure the diameter of the outer cylindrical surface. Their detection objects are mostly smooth surfaces, unlike internal thread addendum gages that directly serve specific parts of the thread structure. This targetedness makes its function unique in the gauge system.
From the perspective of structural design, internal thread addendum gages have structural characteristics that are significantly different from other gauges. Its working part presents a thread profile that matches the internal thread, and parameters such as the tooth profile angle and pitch strictly comply with specific thread standards. This toothed structure is designed to accurately fit the crest area of the internal thread. Common gauges such as smooth limit gauges have smooth cylindrical or flat working surfaces and no complex thread profile design. The difference in structure enables internal thread addendum gages to penetrate into the tooth top of the internal thread for effective detection, while other gauges cannot achieve this function.
In the application of measurement principles, internal thread addendum gages also show different logic. It usually adopts the design concept of go and no-go gauges, and judges whether the tooth top size of the internal thread is qualified by the combination of go and no-go gauges - go gauges should be able to be screwed in smoothly, and no-go gauges cannot be screwed in, so as to ensure that the tooth top size is within the allowable tolerance range. Some other gauges, such as dial indicators, may use direct measurement or comparative measurement to obtain specific size values through pointers or digital displays. The difference in measurement principles makes the detection process of internal thread addendum gages focus more on conformity judgment rather than accurate numerical reading.
The difference in actual usage scenarios also distinguishes internal thread addendum gages from other gauges. It is mainly used in the production inspection of internal threaded parts in mechanical manufacturing, such as the tooth top size control of pipe connectors, threaded holes and other parts. These scenarios have high requirements for the matching accuracy of threads, and whether the tooth top size meets the standard directly affects the connection strength and sealing of threads. Other gauges may be more used for the inspection of basic dimensions such as shaft diameter and hole diameter. The application scenarios cover multiple links of mechanical processing, but unlike internal thread addendum gages, which are closely centered on the specific needs of threaded connections, the targetedness of this scenario makes its function more focused.
In terms of accuracy requirements, internal thread addendum gages often have more stringent standards. Since the accuracy of threaded connections is directly related to the assembly performance and use effect of parts, a slight deviation in the tooth top size of the internal thread may cause the thread to fail to screw normally or affect the reliability of the connection. Therefore, the manufacturing accuracy of internal thread addendum gages must match the processing requirements of high-precision threads. Some other gauges, such as those used for rough machining inspection, have relatively low requirements for accuracy. The difference in accuracy levels reflects the key role of internal thread addendum gages in thread manufacturing quality control, and also puts them at a more stringent level in the gauge accuracy system.
In terms of maintenance, internal thread addendum gages also have their own special features. Because their working surfaces have fine thread profiles, these profiles are easily bumped or corroded during use, affecting the detection accuracy. Therefore, special attention should be paid to avoid contact with hard objects during maintenance, and they should also be placed separately during storage to prevent wear. Other gauges, such as smooth gauges, have simple surface structures, and are more focused on cleaning and rust prevention during maintenance, so the maintenance difficulty is relatively low. This difference in maintenance requirements is essentially determined by the complexity of the gauge structure and the sensitivity of accuracy, and also reflects that internal thread addendum gages need more careful care during use.
From the perspective of the standard system of industry applications, the specifications followed by internal thread addendum gages are also different from other gauges. Its design, manufacture and inspection are usually based on special thread standards, such as the specific provisions of the national standard for ordinary thread gauges, which have clear requirements for various technical parameters of the addendum gauge. Other gauges may follow different standard systems, such as the inspection standards for the dimensions of smooth workpieces. The difference in standard systems requires reference to specific specifications for the selection, use and acceptance of internal thread addendum gages. This difference in standardization further highlights its difference from other gauges in industry applications, and also ensures its accuracy and authority in thread detection.
