All good points, and I, like all of you, still bear the faint scars of early experimentation, and can still remember the fear of the little nick or gash being discovered and the resulting confiscation by mom.

It taught me to be more careful as much (if not more) than the safe handling lectures and demonstrations that I endured.

Of course, our dads didn't have the wealth of information at their fingertips that we do, so as others mentioned, make it an event, be a part of it, have your own knife out and describe what it means to you, etc.

Kids will be kids, he'll be pulling it out and staring out it at every opportunity until he's had it long enough that the allure wears off. I suppose you need to talk about carrying to school, opening it in public (at his age), etc.