Maybe you can add an efficiency column to the chart with the RATIO of the MAX current to MIN current. This could be really useful for multi-cell bits, I believe, because more efficient motors perform better with multiple cells. In this case, the 2.6 rules!
If a motor is doing NO work, than 100% of the power is converted to heat. This can explain why motors get so warm under no load. I
think the maximum heat produced is I^2*R,
where R is the armature resistance and I is the NO LOAD current. Since the current is directly proportional the the voltage, a more efficient motor can run at a higher voltage before overheating.
This is good because the frequency (rpm) is directly proportional to the voltage. Please don't bite my head off if that's not what the tests say... that's just what my physics text book says!
By the way, your idea that current = torque is verified in my physics book too.
