In order for gears to work effectively, and not become damaged, it’s important that the center-to-center distance is correctly adjusted. The gears in DETAIL A, of the figure below, may work under very light load, but they will certainly not work and will skip under any significant loading. The gears in that example are too far apart and so the teeth of each gear barely contact each other. The gears in DETAIL B are correctly spaced and will provide smooth and reliable operation.