Thread is a fastening connection structure widely used in the industrial field. In military models and products, more than 80% of the structural connections are completed through threads. Whether the thread is qualified or not directly affects the assembly performance and safety of the equipment.
In the measurement of thread parameters, according to the different measuring equipment, it can be divided into a variety of thread parameter measurement methods, and one of the most commonly used measuring equipment is the thread gauge.
what is it? How is it used? What are the pros and cons? The answer is in the article below, so let’s get started!
What is a thread gauge
Thread gauges, also known as thread go-no-go gauges and thread gauges, are usually used to check whether the thread size is correct. Thread size consists of thread diameter and pitch. Usually, when selecting a thread gauge, it is necessary to know the thread specification for inspection.
Thread gauges can be divided into thread plug gauges and thread ring gauges according to the internal and external threads to be inspected, and there is also a sheet-shaped tooth gauge. Thread plug gauges and ring gauges are generally used in manufacturing to facilitate quality control, and tooth profile rules are generally used in production.
Thread plug gauge: It is a tool for measuring the correctness of the internal thread size, which can be divided into three types: ordinary coarse thread, fine thread and pipe thread.
Thread ring gauge: used to measure the correctness of the external thread size, one piece for the through end and one piece for the stop end.
Tooth gauge: A set of tooth gauges includes commonly used tooth shapes 0.5/0.6/0.7/0.75/0.8/0.9/1.0/1.25/1.5/1.75/27, and the tooth pitch of the unknown thread can be confirmed by matching the tooth gauge with the tooth shape .
According to the subdivision of the use occasion, it can also be divided into: work rules, acceptance rules, proofreading rules and benchmark rules.
Working gauge: Thread gauge used to manufacture and inspect workpiece threads.
Acceptance gauge: The thread gauge used by the inspection department or user representative to accept the workpiece thread.
Calibration gauge: thread gauge used in the manufacture and inspection of working gauges. For cylindrical threads, usually only the calibration plug gauge is used for the inspection of the working ring gauge. Some tapered threads (such as special threads for petroleum) have calibration plug gauges and calibration ring gauges, which are used to check the working ring gauge and working plug gauge respectively.
Reference gauge: Certain conical threads (such as oil drill pipe joint threads and NPT threads) require reference gauges for checking calibration gauges.
How to use thread gauge
Before use, it must pass the inspection and measurement of relevant inspection and measurement institutions before it can be put into production site use.
When formally used, it is necessary to confirm that the tolerance level and deviation code of the measured thread are the same as the tolerance level and deviation code marked on the ring gauge.
Secondly, clean up the measured thread oil and impurities, and then after the ring gauge is aligned with the measured thread, use the big thumb and index finger to turn the ring gauge, and the screwed-in thread length is within 2 pitches, otherwise it is judged as unqualified. Qualified product.
When using a cylindrical thread gauge to inspect the thread, the through-end thread gauge should be completely screwed in and pass through, and the stop-end thread gauge should not be screwed in or
If part of the thread is allowed to be screwed in, the thread to be inspected is qualified. When a dispute arises, it shall be dealt with in accordance with relevant regulations.
When using a tapered thread gauge to inspect the thread, the following points need to be paid attention to: use the limit gauge to inspect the measuring surface of the thread to be inspected (the internal thread is
Whether the position of the large end, the external thread is the pipe end plane) is within the specified upper and lower limits; use standard gauges (such as oil-specific thread
gauge) to check whether the measuring surface of the tested thread is within the specified range (whether the tight distance of the oil-specific thread is qualified). dry stone
For oil-specific threads, it is also necessary to check whether the individual elements of the thread are qualified.
Advantages and Disadvantages of Thread Gauge
The advantage of this test method is fast, economical and practical. For enterprises with a high level of production technology, the use of qualified thread forming tools and special thread processing equipment (such as thread taps, dies, thread rolling machines, thread rolling machines, etc.) can better control the quality of threads.
The main disadvantage of this inspection method is that it can only qualitatively check whether the pitch diameter of the thread is qualified, and can only know whether the pitch diameter of the thread is between the smallest single pitch diameter and the largest active pitch diameter, and cannot know the specific value of the thread size. Parameters such as half-angle error, pitch error and various shape errors cannot be quantitatively controlled separately.
Hope the above content can help you.
