FadedFrontiers They are 4 pole induction motors so at 50Hz will run at a theoretical no load speed of 1500 rpm. In reality there are losses and slip, so usually around 1450 RPM. The speed is controlled by mains frequency, which is a remarkably consistent value to avoid damage to the grid. In America at 60 Hz they spin faster, usually around 1750 RPM.
Under load the motors will actually spin a little bit slower due to increased slip. From grinder to grinder they should really be very consistent because it’s more the mains frequency and number of poles that are important, nothing particular about the motor itself.
