### fHβ

fHβ is a symbol used by your gear standard. It specifies the distance between two design helices which intersect the mean helix at the extremities of the evaluation range. The helix angle deviation is positive when it increases the absolute value of the helix angle, and negative when it reduces it. In the case of spur gears, deviations are always positive. Their direction is identified by an index 'r' (in the sense of a right-hand thread), or 'l' (in the sense of a left-hand thread). Please see the appropriate gear standard for a detailed definition of this value.