herringbone gear, a proper term

[NikonD]

Hi!
I wonder whether there is a conventional term for those single-helix halves of a herringbone gear?
Such a gear includes two helices, doesn't it? Each of the two occupies half the gear. Is it herringbone semi-gear or semi-herrinbone gear or anything else?
OK. I just need to know how you'd term it in English.
Hope somebody knows the answer.

 

[EnglishMuffin]

Since a herringbone gear is effectively nothing more than two helical gears of opposite hand joined face to face, I fail to see how "half a herringbone gear" could be anything other than a helical gear. Sometimes herringbone gears are truly made from two separate gears, and sometimes they are one piece components, cut with a special shaping process.

 

[Carburize]

The progression?
1)Spur gear
2)Single helical gear
3)Herringbone gear
4)Double helical gear - (herringbone gear with an apex gap)

Each herringbone or double helical gear has a left hand and a right hand helix.