Loose Square Drives, Not Lost Corrections: What Five Out-of-Tolerance Torque Transducers Revealed

An aerospace and defense customer sent Morehouse six square-drive torque transducers, and five of them failed their ±0.1 % tolerance as received. Their metrology lead wanted to know whether the design was unreliable, operators had over-torqued the units, or the stored corrections had been lost. The calibration data told a different story. The errors changed with loading direction, grew at low torque, and jumped from point to point, which is the signature of loose square drives, not a sensitivity shift. On five of the six units, one count of the indicator used up the entire tolerance at the first test point. This case study shows how Morehouse read the pattern behind these out-of-tolerance torque transducers and the practical fixes any torque lab can apply, from drive verification and repeatability studies to a better interim check standard.