Fig 8Herringbone gearsdrag to turn · click to pausetwo helices, thrusts cancel
DriverTwo helical gears of opposite hand, joined face to face, so every tooth is a V. Each half pushes along the shaft, but in opposite directions, so the thrusts cancel inside the gear and the bearings see none. You keep the smoothness of a helical gear without the thrust bearing. They are harder to cut, because the cutter can't run straight through, so many have a groove in the middle.