Abstract: A retainer for axially retaining a cutter on the journal pin of a rotary drill bit body includes a plurality of arcuate sliding keys and a single initial tensioning ring accommodated astride an annular groove formed in the peripheral outer wall surface of the journal pin and a corresponding annular groove formed in the inner peripheral wall surface of the cutter. When the cutter is mounted on the journal pin, the initial tensioning ring functions to urge the sliding keys into pressured contact with the cutter groove when the two grooves are in registration. Not only is assembly facilitated, but damage to the sliding keys that might otherwise be caused by any excessive axially directed force applied to the sliding keys during operation of the drill bit is prevented by allowing the sliding keys to recede within the annular groove of the journal pin.

Abstract: A rotary shaft seal for the rotary cutter of a each boring drill bit includes a fixed seal ring fitted securely in the cutter and having an end face which includes a first tapered surface, a floating seal ring having an end face, which includes a second tapered surface opposing the first tapered surface, and a curved inner circumferential surface, and a resilient O-ring compressed between the curved inner circumferential surface of the floating ring and a bearing portion on which the cutter is rotatably journalled.

Abstract: A pressure compensator installed in the bit body of a rotary earth boring tool to lubricate the bearing surfaces of a rotary cutter and to effect a liquid seal. In order to reduce the number of component parts and to enhance durability, the pressure compensator includes a rubber diaphragm interposed between upper and lower capsule halves that form a spherical space.

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.