Self harm

I've recently got into cutting my arm. Not to kill my self. I'm not even particularily depressed at the moment. Its more just to see how far I can go. It started off as barely surface scratches and they're gradually getting deeper but it doesn't hurt. I have a very high pain tolerance and if I concentrate hard I can turn off pain altogether in any situation. So even though I don't feel the pain, the reason I build up the depth gradually is that I don't like the feel it makes as your doing it. Its like the sound of chalk on a blackboard but a sensation. It rips rather than tears smoothly. Bit annoying. O well I'll keep trying.