|4551050||Threaded engagement means|
According to a depicted embodiment thereof, the novel threaded engagement means comprises a drill rod coupling which is centrally bored and threaded to receive threaded drill rods. A stack of apertured discs, however, engages and lines the threaded bore. ...
|4413689||Plural-part earth bit, and an improved bit head therefor|
According to a depicted embodiment thereof, the novel earth bit comprises a shank having a threaded end and a bit head centrally bored and threaded to receive a shank. A stack of apertured discs, however, is interposed between the threaded bore or cavity ...
A rotary spindle of a drill mount has a free end provided with a thread whose angle of rise is so selected that its tangent is at least equal to the coefficient of static friction of steel on steel....