The NPT thread gauge has tapering ends to enable dry sealing

No industrial manufacturing activity is complete without the use of screws, nuts, and bolts. These might look very small items, but they have great importance in any manufacturing industry. No machine is complete without the screws, nuts, and bolts to hold them from falling apart. Have you noticed that these screws and nuts have threads? It is important to ensure that you use the right size of screw or bold to affix machine parts. The usage of a wrong screw can result in malfunctioning of the machine and may have disastrous repercussions as well. You have different kinds of equipment to measure the pitch of the screws. You call them gauges. Depending on the usage, you have different kinds of gauges such as NPT thread gauge, ACME thread gauge, UN Thread gauges, etc.

Let us now look at some of these different kinds of gauges in brief.

NPT Thread gauge: Pipes are equipment that can have both internal and external threads. These pipes have use for transporting liquids as well as gases. Hence, one has to be very careful while joining them. There should not be any leaks anywhere. This makes the role of the gauges very important. The NPT gauge (National Pipe Thread Gauge) is the standard gauge for measuring the pitch of the threads in a pipe. You have the plug gauges to measure the pitch of the internal threads whereas a ring gauge will help in measuring the outer threads.

Using a NPT thread gauge is very easy. Every gauge has two parts, the Go and the No Go part. If the Go thread goes into the threaded hole easily and the No Go thread does not, the product is considered to be within the tolerance limits

Where do you use a NPT thread? The NPT thread is used in the US and Canada alone because these countries are the only ones today following the UN measuring system. All other countries in the world have shifted to the metric system.

The NPT threads have a tapering system whereby they form a kind of a seal when you torque it. The threaded body is tapered and thus a larger diameter keeps compressing into a smaller one thereby forming a kind of a seal. This is very important especially in pipes that transport combustible gases and volatile liquids. A thread seal tape is enough to seal the NPT fittings. The other use of the tape is that it prevents the corrosion of the threads.

You have another kind of thread known as the NPTF threads. They are also known as Dryseal American National Standard Taper Pipe threads. You do not require any type of sealing that you normally use for other types of threads.

The plug gauges have utility in measuring the pitch of the internal threads whereas the ring gauges do the same for the external threads. No one can underestimate the use of ring and thread gauges in the manufacturing industry. They have the greatest importance of all other machinery items.

Frank Xu is the author of this article on Trapezoidal thread taps.

Frank Xu is the author of this article on Unef thread gages.Find more information, about UN thread gauges here