Thread four is a kind of industrial pipe fittings, its main function is to pass through the medium to carry on the shunt. The thread four passes can be divided into forging and casting in the production process. Forging refers to the thread processing on the lathe after the ingot or round rod is heated and forged into shape. Casting refers to the molten steel ingot poured into the model of the four passes and then cooled.

Because the manufacturing process is different, the size of the pressure is different, forging pressure is much higher than casting.

The main manufacturing standards of thread four-way are GB/T14383, ASME B16.11, BS 3799.