Blast hole drill pipe gripping mechanism

A method of loosening a threaded joint between a first member and a second member that is prevented from rotating, comprising:

• advancing one end of an arm having a grip into contact with one side of the first member;
• advancing a jaw having a grip into contact with another side of the first member to clamp the first member between the grips;
• applying a force to further advance the one end of the arm while applying a second force to retract an opposite end of the arm to rotate the first member;
• and
• releasing the contact of the grips with the first member.

A method of loosening the threaded joint between members of a drill string in which one member is held against rotation, comprising:

• pivoting one end of an arm about its second end to advance a grip into contact with one side of the other member;
• pivoting a jaw having a grip about a pivot on the arm to contact the grip with another side of the other member;
• and
• continuing to pivot the one end of the arm while moving the second end in a direction about the other member that is opposite to the movement of the one end about the other member.

A mechanism for loosening a threaded joint between a first member and a second member held against rotation, comprising:

• an arm having first and second ends and a grip;
• a jaw mounted for movement on the arm and having a grip that can oppose the grip on the arm;
• first means for advancing the first end of the arm to engage its grip with the first member and for further advancing the first end of the arm;
• second means for moving the jaw to engage its grip with the first member;
• and
• third means for retracting the second end of the arm while the first means is further advancing to apply a moment to the first member.

A mechanism for loosening a threaded joint between first and second members of a drill string, comprising:

• an arm having first and second ends and a grip engageable with the first member;
• first and second hydraulic cylinders pivotally connecting the first and second ends of the arm to a common support;
• a jaw pivotally mounted to the arm intermediate its ends and having a grip engageable with the first member;
• and
• a third hydraulic cylinder connecting the jaw to the arm to pivot the jaw.