A face gear transmission is an angular transmission (typically 90°), in which the axis angle can be chosen freely in the range of 0º to approximately 135º . The pinion is a standard cylindrical gear, with either spur or helical teeth. The geometry of a face gear transmission is frstly determined by the pinion geometry. Additionally, the axis angle and the gear ratio set the face gear geometry. Since there is a difference in rotational speed on the inside and outside diameter of the gear, the pressure angle alters over the tooth width. However, there is always a line contact between pinion and face gear, even with spur teeth, in which the lines of contact run helically over the tooth fanks, therefore generating a high total contact ratio and low noise levels. The cylindrical pinion can be moved freely in the axial direction over the face gear teeth, without affecting the contact pattern or backlash.