Go and no-go gauges are a type of gauge, which are divided into go gauges and no-go gauges. Go gauges are used to check the maximum limit size of threads to ensure that the threads can be screwed in smoothly; no-go gauges are used to check the minimum limit size of threads to ensure that the threads are not too loose.
Preparation before testing
1. Select a suitable go and no-go gauge: According to the thread specifications of the bolt, including nominal diameter, pitch, tooth angle, etc., select a matching go and no-go gauge. For example, metric threads and imperial threads should use corresponding go and no-go gauges, and threads with different pitches also need go and no-go gauges with different pitches.
2. Cleaning: Use a clean cloth or brush and other tools to remove impurities such as oil, iron filings, burrs, etc. on the surface of the bolt thread. At the same time, clean the measuring surface of the go and no-go gauge to ensure the accuracy of the test.
3. Check the go and no-go gauge: Check whether the go and no-go gauge is damaged, deformed, rusted, etc., to ensure that the go and no-go gauge itself has no quality problems. You can also gently turn the spiral thread of the go and no-go gauge to check whether it is flexible.
Inspection operation steps
1. Through gauge inspection: Align the through gauge with the bolt thread, so that the axis of the through gauge coincides with the axis of the bolt thread, then gently apply axial force and slowly rotate the through gauge. If the through gauge can be smoothly screwed from one end of the bolt thread to the other end without jamming or locking, it means that the thread diameter and other dimensions of the bolt are not less than the minimum limit size, and the through gauge inspection is qualified.
2. No-stop gauge inspection: After the through gauge inspection is qualified, the no-stop gauge inspection is performed. Similarly, align the no-stop gauge with the bolt thread and screw it in slowly. Under normal circumstances, the no-stop gauge should not be screwed into the bolt thread for more than 2 turns or 2 pitches. If the no-stop gauge cannot be screwed in after reaching the specified number of turns or pitch, it means that the dimensions of the bolt thread diameter and other dimensions do not exceed the maximum limit size, and the no-stop gauge inspection is qualified.
Inspection standards and judgment methods
1. The through gauge passes the no-stop gauge: that is, the through gauge can be smoothly screwed into the bolt thread, and the no-stop gauge cannot be screwed in or does not exceed the specified number of turns, then the thread size of the bolt is judged to be qualified.
2. Both the go gauge and the stop gauge fail: It means that the bolt thread size is too small or there are serious shape errors and defects, which result in that the go gauge and the stop gauge cannot be screwed in normally, and the bolt is unqualified.
3. Both the go gauge and the stop gauge pass: It means that the bolt thread size is too large, beyond the tolerance range, and the bolt is unqualified.
Inspection precautions
1. Temperature influence: The inspection environment temperature is best controlled at the standard room temperature of 20℃±2℃ to avoid measurement errors caused by thermal expansion.
2. Humidity conditions: Generally, the relative humidity of the inspection environment is required to be controlled at 40%-60% to prevent rust and corrosion from affecting the inspection accuracy.
3. Operation force: Avoid excessive force during operation to avoid damaging the bolt thread or the go and stop gauge.
4. Regular calibration: The go and stop gauge is a precision measuring tool and needs to be sent to a professional metrology agency for calibration regularly. It is generally calibrated every 1-6 months according to the frequency of use.
Post time: Feb-11-2025