Definitely do this. I used to drive through NYC a couple of times a month and didn’t know the knife I had with me could have been considered illegal. I say could have because the laws there are so vague that it is up to the judge to make the final call. There are knives you can legally buy in NYC that are illegal to possess in NYC.
Something to consider about knife attacks is that it isn’t just about the knife but the attacker. You could probably divide attackers into three categories: the pro, the amateur and the psycho. In my experience, I’ve found that defense tends to focus on attacks by “pros.” For example, I’ve seen a trainer tell someone playing the attacker he was holding the knife incorrectly. “No one would use a knife like that.” Yeah, a pro wouldn’t hold a knife like that but a pro wouldn’t let you see the knife until it was in you anyway.
The reality is that if you are attacked by someone with a knife they won’t be experts. It will either be an amateur (for lack of a better word) who will usually slash rather than stab or a psycho who will usually stab and stab and stab. The thing about stabbing a human is that is a lot easier for the knife to go in that it is to pull it out. Psychos are able to stab dozens of times because they are, well, psychos. This is why a pro will only stab you once. And when I say psycho it could also mean so overcome with anger they are temporarily insane.
In my hometown a young girl was stabbed to death, in front of her mother and perhaps hundreds of people, in broad daylight in the street during a street fair. The killer was a man who walked off the grounds of the mental hospital. He bought a knife, walked out of the store, and attacked the first, weakest target he saw. I know people who witnessed it and one of them is a big guy and he told me how he was wearing his work boots when he kicked the guy in the head (he was kneeling over the girl as he continued to stab her) and the killer just looked up at him as he continued stabbing. I bring this up for a couple of reasons: one is that self-defense should include defending others. In other words, how do you stop someone who is attacking someone else? How do you disarm them if they are using a weapon? The second reason is that it isn’t the just the knife but the attacker. This person I brought up was very mentally deranged. Some fancy disarm technique that supposedly will work against someone who attacks in a “professional” manner won’t work against someone who is crazy (and you can include someone on drugs).
On a side note, according to an ancient Roman text on military training, people instinctively slash when given a bladed weapon. Thus, part of the training was to teach recruits to stab. A normal person’s instincts is to use a less than lethal technique. Probably because a normal person is thinking about protecting himself more than killing the other person. That takes another level of commitment.