Types of Threads
R Thread according to EN 10226-1
R threads are the first standardized threads in the world. They are also known as Whitworth threads or inch threads. The name Whitworth goes back to Sir Joseph Whitworth, who introduced the R-thread.
R threads are tapered / conical on the outside. If they are cylindrical on the inside, they are called RP threads. They are used for pipes and fittings that are sealed in/by the thread. There are sealants such as PTFE tapes which can be used.
Thread angle 55°
The thread identifier describes the diameter of the threads in inches. e.g., G 1/8, G 1/4 etc.
G Threads according to ISO 228/1
G threads are also called Whitworth parallel threads. They are cylindrical on the inside and outside. They are suitable for pressure-tight connections which are not sealed in/by the thread - therefore they are not metallically sealing. Here sealing rings are used.
Thread angle 55°
R and G threads can be combined, but ...
...G male threads (cylindrical) can only be screwed into G female threads.
...R male threads (tapered) can be used in G or R female threads.
NPT Threads according to ANSI B1.20.1 (NPT = National Pipe Taper)
NPT threads are conical on the inside and outside. They can be found in pressure-tight (self-sealing) threaded connections that are sealed in the thread. There are sealants such as PTFE tapes which can be used.
Thread angle 60°
Important terms for threads
The following list provides important terms for threads. (German meaning)