Abstract: A gauge device has an insert portion having means for aligning the insert portion along a longitudinal axis of an oil drill pipe so that the squareness of a joint shoulder and shoulder available for grinding at a box end of an oil drill pipe can be determined. The insert portion has indicia formed thereon calibrated to read the shoulder available at the box end of said drill pipe. An indicator portion of the gauge device is slideable along the insert portion and has a radially directed annular flange extending perpendicular thereto and perpendicular to a longitudinal axis of the oil drill pipe upon insertion of the insert portion within the box end of said oil drill pipe. The squareness of the outer shoulder of the oil drill pipe can be directly visualized by reference to the annular flange of the indicator portion. Field grinding can then be performed on the box end of the oil drill pipe until a square shoulder is obtained.