The best way that I have found is to create a helical or bevel or any type of gear for that matter is to create a surface (quilt) of the tooth form on a make datum and pattern the form depending on what type of gear you are producing. The patterned surface can take advantage of some of the more advanced surface creations such as var section sweep (very useful for crown bevel gears). Once you pattern the surface you can use cut on quilt and ref pattern the cut.