There is no reason a person needs to own a knife and there is no amendment protecting the ownership of knives. Most homes in America have tens to hundreds of knives. Cutting devices make no sound so the threat is even greater than firearms.
Per the FBI crime statistics there is at least 5 times more death by knifes than rifles
With more and more gun regulation in the US, we need to get ahead of the epidemic as seen in Europe as per pages 39-40 of the UN's Global Study on Homicide.
There have been many mass school killings by cutting devices around the world as seen in Japan and China