API round thread root-to-apex clearance is 0.152mm;
In addition to poor sealing performance, API round threads have low tensile strength.
Under normal conditions, the API round thread has a tensile strength of only 80% of the strength of the pipe body. Under the action of biaxial stress such as external pressure and axial tension, slippage easily occurs when encountering large bending or impact loads.
The basic shapes of all casing round threads and coupling threads are the same, and the basic dimensions and tolerance ranges of tooth height, pitch, taper, and profile angle are exactly the same. And the requirements of the arc shape of the tooth tip and the tooth bottom, the outer chamfer of the pipe end, and the disappearing taper angle are the same.