The present invention relates to nozzles for use in drill bits and particularly to nozzles having an internal passage that is offset at an angle from the longitudinal axis of the nozzle. More particularly, the invention relates to a method and apparatus for properly aligning the outlet of the internal passage relative to the drill bit.
In rotary drilling operations, a rotating drill bit cuts soil and rock as it is advanced through the rock formation. The cuttings are flushed away from the drill bit and up the borehole by high pressure drilling fluid supplied through a passage in the drill stem. The drilling fluid is directed outwardly from the drill bit through nozzles in the face of the drill bit.
Typically, the nozzles are retained in the drill bit by male threads on the nozzle. The threads are screwed into matching female threads in the body of the drill bit until the nozzle bottoms out. As long as the nozzle is cylindrical in shape and no specific angular orientation is needed, a conventional nozzle is functional.
Some nozzles used in drill bits are non-symmetric and require precise orientation in the drill bit. However, because of uncertainties in thread position, or clocking, in both the bit and the nozzle, it is impossible to predict in advance what the angular position of the nozzle will be when it is threaded into the drill bit until it is fully seated. Thus, some type of field adjustment is necessary.
A conventional approach to providing field adjustment, such as disclosed in U.S. Pat. No. 4,533,005 to Morris and U.S. Pat. No. 4,776,412 to Thompson, is to provide a threaded ring around a nozzle body that attaches the nozzle to the drill bit. The nozzle body is rotatable relative to the threaded ring after the ring is seated in the drill bit which allows the nozzle to be properly oriented within the drill bit. Unfortunately, the conventional approach requires the use of special tools in the field, which is inconvenient and expensive. An additional disadvantage is that, if the threaded ring begins to back out of the drill bit, the nozzle body is free to rotate within the ring relative to the drill bit and thereby lose the proper orientation.