This guy might know a few things about knives, but he is not all that smart when it comes to "survival". His thinking that cutting toward the chest with a knife is ok if you can control the knife is just plain stupid. When i was a kid everybody always said "Never carve toward yourself!" Then, a friend of mines dad pulled the smooth move of using a pen knife to carve out a bolt hole in a door by cutting towards his chest... OOOPS!!! Stuck the knife right into his chest over his heart. His last words as he was being loaded into the ambulance was "I always told my son to never carve toward himself..." Lucky for him he was using the little 1 inch blade on the knife and "only" just pierced his heart. Needless to say, we little kids learned our lesson well from his experience. He did live.
Hey, what's a quicker way to die? Sticking yourself in the chest with a knife or slicing through your thigh?
As for cutting down 6 inch trees with your little 4 inch blade knife... i got to ask; "What the hell for?" To me that sounds like a tremendous waste of energy when you are "trying to survive". It might be a better idea to think a little harder and come up with a better way to do whatever it is you NEED to do. Again, what do you need a 6" thick tree for? Are you planning to stay for a while or do you just need to get out of the rain till morning and then hump it toward home? If you are trying to get firewood, why beat on your poor little knife and potentially damage it trying to make kindling when you could probably much easier gather a bunch of little sticks and leaves and grass or whatever and start a fire. Usually there will be a big enough rock (about 10-40 pounds) that you can pick up and smash against a good size branch you've leaned against a tree or another big rock and break it into various size pieces with one blow. (Hint: Pick up the rock and throw it down like King Kong... remember to let go of the rock and get out of the way!") Save your energy for staying warm, starting a fire, finding food/water, and getting the hell out. If you planning to stay for a while because you basically have no choice, it is better to build a light shelter that is strong and keep adding insulation as time goes on and stick to the basics of finding food, water, and warmth. Trashing your knife or yourself is not going to help.
Rant off.