Try the book "Gears and Gear Cutting" by Ivan Law. It gives a lot of information about how to do gear cutting in a home shop without all the fancy commercial equipment. I can't remember offhand if it talks about helical gears, but I know it does explain how to do bevel gears, which of course are also quite a challenge.
Try to make a living, not a killing. -- Utah Phillips
Don't believe everything you know. -- Bumper sticker
Everybody is ignorant, only on different subjects. -- Will Rogers
Law of Logical Argument - Anything is possible if you don't know what you are talking about.