Does anyone know of a cad program that can be used to design a wormgear that has a gradual increase in it's pitch the longer it is. The gear I am looking to design will have a 2" diameter, and be approximately 2' long. It will have a starting pitch of about 1/4" on one end and gradually increase to about 3/4" on the other end. Any design help would be greatly appreciated. Thanks...Andy.