I can find the answer to this all over the web but no-place that gives me enough specifics to actually make the measurement.

I know that torque is (more or less) proportional to current. The motor data sheet gives me a torque constant of 0.62 Nm per amp. So far, so good, but which amps? Is that the instantaneous peak DC current in one winding with the others unexcited? Is it the sum of the instantaneous DC currents? Is it the instantaneous current in the q axis as projected from the shaft angle? Is it the RMS current? If so, is it the RMS current in one wire or in one winding (which is not necessarily the same in a delta-wound stator)?

Short version: I clamp an oscilloscope current probe on one wire and read the current waveform. How do I get from here to torque? The current is approximately sinusoidal with a peak of about 6.3 amps. The RMS current, as computed by the 'scope is about 4.8 amps.