Herringbone gear
（重定向自Double helical gear）
![](/Images/godic/202501/09/Engrenages_-_85.488_-0915.jpg")
![This double-helical bevel gear was made by Citroen and installed around 1927 in small Miřejovice hydropower plant on Vltava in the Czech Republic, connecting a Francis turbine to the generator. It worked flawlessly until 2011.](/Images/godic/202501/09/Double-helical_bevel_gear_Citroen0915.jpg")
0915.jpg")
A herringbone gear, a specific type of double helical gear, is a special type of gear that is a side to side (not face to face) combination of two helical gears of opposite hands. From the top, each helical groove of this gear looks like the letter V, and many together form a herringbone pattern (resembling the bones of a fish such as a herring). Unlike helical gears, herringbone gears do not produce an additional axial load.