That looked great Shawn.
I was once stuck without a cutter and used a knife, but a little differently than that. I didn't trust the sharpness of the knife to try a straight cut, and didn't think to try what you did. Instead, I used the point of the knife to cut a circle in the cap, similar to what a punch would do.
It certainly wasn't as clean a job as what a punch could do, but it worked well enough in that situation.
Well done.
PS Nice looking knifes you have, and SHAWN NEEDS A NEW CUTTER!!!!