The main shaft of the step motor is very tight, and the hand can't move when it is not energized
The normal step motor can be rotated by hand under the condition of power failure. You say that the main shaft step into the motor is different, generally vertical installation, with the brake, so the power failure condition can not move. Of course, if the machine does burn down the card, it will not move. To sum up, can't say "do not use the hand to turn the hand without the power" to think the motor must be bad.
Motor bad not bad, only by using or testing the resistance know, generally in the stepper motor magnetic steel, magnetic steel has magnetic, have certain lock axial force (electric field). The motor will be more relaxed after the magnetic attenuation, and the step motor has a feature, if a set of winding is short. The electrical opportunity lock shaft (and no electricity), the step motor can also be used as a generator.
No electricity is a lock. The motor will generate an electric current, so no force will be turned
