R-thread

What is an R thread?

The R thread is a type of Whitworth system pipe thread, widely used especially for pipe connections. It’s also known as the BSPT (British Standard Pipe Taper) thread. In an R thread, the external thread is tapered, allowing for a self-sealing joint without the need for separate gaskets. The internal thread can be either cylindrical (Rp) or tapered (Rc).

Characteristics of the R thread

The defining feature of the R thread is its 55-degree thread angle, based on the Whitworth profile. The number of threads per inch varies by nominal size; for example, an R 1/8" thread has 28 threads per inch, while an R 1" thread has 11 threads per inch. The thread's taper ratio is 1:16, which means the thread tapers by one unit for every 16 units of length.

Use of R threads in the engineering industry

In the engineering industry, R threads are commonly used for piping and hydraulic system connections. Its tapered shape enables tight and durable joints without additional sealing materials, which is particularly important in high-pressure systems. R threads are also used in pneumatics and other applications where reliable pipe connections are required.

Differences between R and G threads

It’s important to distinguish between R threads and G threads. While both are based on the Whitworth profile and have the same thread angle, their geometry is different. The R thread is tapered and self-sealing, whereas the G thread is cylindrical and does not seal on its own, requiring a separate gasket such as an O-ring for a leak-tight connection. Mixing these threads can lead to leaking joints and other issues.

Summary

The R thread is a tapered pipe thread conforming to the Whitworth system, widely used in the engineering industry, especially for pipe connections. Its self-sealing feature makes it a popular choice in applications requiring reliable and durable joints. It’s essential to distinguish the R thread from the cylindrical G thread to ensure proper sealing and connection integrity.