Herringbone gears

Herringbone gears have all the advantages of helical gears in that they are strong and quiet, with the added advantage of being able to cancel thrust forces by combining helical gears with both right and left twist. On the other hand, they have the disadvantage of being difficult and expensive to manufacture. Herringbone gears do not create such a large aksial force in the transmission as helical gears. The opposite effect of forces cancels it out.