Helix angle on drawing

The helix of a helical teeth should, regarding direction and dimension, always be shown in a view, never in a cross-cut. Besides other indications it can also be pointed out by written text, e.g.: right-helical gear, helix “X °”. The figure here above “A” shows a wrong way of indication.


The helix of helical angle is the angle of the helix on the cylinder that has as a basis the pitch circle relative to the shaft line or of a mantel line of this cylinder. The descriptive helical lines on other parts of the tooth flank have another angle which, however, never should be indicated. When searching for the angle value of an existing helical gear one can calculate the helix angle at the reference cylinder based on the angle on the tooth tip; the latter can be measured with an angle gauge when the gear is being rolled on a piece of paper and so a pure print is obtained. However, this measurement is delicate and the result is not very reliable; we recommend to leave it to us for looking for the right angle as we have the necessary tools.