Abstract: A composite nozzle for a drill bit and a bore enlarging bit, the body of the nozzle, which is adapted to discharge water toward rotary cutters, being fabricated from a ceramic. The nozzle has a bottom surface which is provided with a high-impact metal plate, and a circumferential wall portion also provided with a reinforcing plate.

Abstract: Pipe joints for a large diameter casing, which are lowered inside an oil well or the like and are successively connected to one another, are subjected to critical conditions such as load on the casing when suspended, and pressure. A pipe joint of this class is also required to provide torque during the connecting operation and sealing capability after connection. Tooth profiles or thread configurations formed in the pipe joints welded to the intervening large diameter tubular member extend over at least three sections. In the first section, each of the external threads is engaged with each of the internal threads in such a manner that its crest and root are fully meshed to allow its butt face to abut against its back pressure face. In the second section adjacent the first section, the threads are so formed as to involve an easy transition to the thread configuration formed in the third section where the threads are so shaped that the external threads are readily meshed with the internal threads.