Whittling wood becomes much more enjoyable once you become very aware of, and can use your knife in complete harmony with the wood being whittled. After practice and experience you'll find out that both the knife and the wood being whittled can be manipulated to achieve a very controlled cut.
In the above photo, the knife is held firmly against the wood, while the wood is "turned" into the knife blade. In this photo a spiral being cut into the wood. To achieve this cut, hold the knife blade firmly against the wood on an angle; then rotate the wood into the knife blade. Keep on rotating/turning the wood into the knife blade while maintaining the same angle of the blade to the wood. Keep doing this until you reach the bottom tip of the wood piece. The cut that results is a spiral stop cut. Next you can follow the spiral stop cut and remove chips, to create a finished spiral, much like an exaggerated screw thread. If this spiral stop cut is made correctly, the knife blade will never slip off the wood and perhaps cause an injury.
This spiral cut can be used on Christmas tree ornaments.