Since the inception of manufacture of industrial equipments, every few months a periodical inspection is done to make sure the components or parts involved in the process meet the required specifications. This has led people to discover several types of quality control tools. Several thread plug gauges, thread gauges and ring gauges have been introduced that are very useful for this application and function which includes height, depth, ring, bore, plug and snap gauges. Gauges according to my opinion are the simplest kinds of tools there are. They are used for ensuring adherence to specifications. Plug gauges for more than decades have been a crucial part in maintaining tolerances of the highest standards.
Thread plug gauges are mainly used to inspect several product lines as a result of their end of use. It assesses the continuity of objects to the prescribed descriptions. A typical thread plug gauge is one whose ends are carefully designed so that one end becomes the upper limit and the other end becomes the lower limit. Plug gauges in the market are available in plain or threaded forms. Typically plug gauge manufacturers focuses on developing only one type of solution and not both.
Since I had already completed my engineering and got a job I asked my brother who was already an engineer to teach me all he knew about thread gauges and thread ring gauges. Thread gauges in the most basic terms are devices used to identify pitch or turn per inch also known as TPI. The pitch gauges are accurately notched metal blades that match with the turns per inch of different types of threads and thread pitches. The thread ring gauges are used to measure how accurate the threads are of the outer surface of rods and pipes. Plug gauges as mentioned above functions to check the conformity of the threads tapped inside holes.
A person who is new to the inspection and metrology of threaded parts finds the plethora gauge types quite amusing. A thread ring gauge can also have different types. In an adjustable thread ring gauge the gauges are ring shaped but they have a split and an adjusting locking screw facility to finely adjust their right gauging size. In a solid thread gauge although it is used to check the level of acceptance of a screw that is the externally threaded part. These again are classified into- a GO and a NO GO thread gauge. These two rings are normally two separate pieces. Thread ring gauges are used to check the accurateness and correctness of the thread to include the thread depth and the pitch diameter.
For the acceptance of the part you must make sure that the GO ring gauge goes through the entire length of the screw without using too much force. Ideally the screw should thread completely through the gauge if the process is done with precision and accuracy. The NO-GO ring gauge can at the very best enter the screw over not more than two rotations and not go any beyond.