Although interesting, I believe this is a very dangerous proposition.

From the way you are asking the question, I believe that you have zero experience in helicopters and much less in RC in general.

Why don't you pair up with an experienced modeler to help you along? Or you could buy a ready made helicopter and reverse - engineer it.

After 20 years of flying helicopters, if I knew anything about lathes, milling, and any kind of metal machining, I may give it a try.

Rafael