The fact that you persist in ignoring the recommendation to buy a meter and then have the gall to tell us you think this method is BETTER than actually MEASURING the current ( and voltage) confirms that your future in electronics will be fraught with problems. I can only say this does does not say anything good about your judgement . The fact that the A4988 will work right out of the box without doing the calibration is not the point. Whether or not you can adjust the pot to some point that allows the motor to work is also not the point. The point is that in your inexperience and twisted logic you actually think that doing the calibration blindly is better than measuring the parameters in question is what sends a red flag about your judgement. Had you simply stated, "I need to be able to use the motor immediately so I'm going to adjust the pot to some arbitrary value where the motors will work and then buy a meter at the first opportunity" there would be nothing wrong with that. It's your outright refusal to buy a meter and insistence on calibrating it without one and at the same time saying you think it's better not to use a meter that puts your judgement in question.