Any rotation will only have gaps, but some gaps are very small. But when these gaps are accumulated together, they cannot be ignored. There are many gears in the structure of the dividing head. Gear transmission is theoretically toothless backlash, but in fact it is very small. If the dividing head always rotates in one direction, error accumulation will occur. For a large number of equally divided parts, the correct use method should be to turn the handle, such as equally dividing 12 parts, not 30 degrees, but first equally dividing 120 degrees, and then dividing 120 degrees into 60 degrees and 60 degrees until.