It is a rarity for me to use pens such as this but the idea of carving a pen was too intriguing to pass up. It was so much fun! Like you, Jen, I still have my Girl Scout knife and I carried it from the third grade until I started teaching. I still have it. 

Here is the picture of the first two pens I carved, along with the knife I used to carve them.

I had neither the tools you used for the project nor the spare funds to go buy specialty drills, etc., so I grabbed a trusty pocket knife and not only did the carving but also "drilled" the hole and made the notches. 

My bamboo didn't appear to be as sturdy as what you used but it was all my garden center had and here are the writing samples the pens produced. My pens may not last as long, but they work.

First pen sample.

Second pen sample.

 

I have more bamboo and plan to make more pens. However, this project was so delightful that I'm thinking of starting a carving project. It's been ages since I sculpted a little donkey out of soap or wood.

Thank you so much, Jen. You opened a whole new area for me to consider.

Addendum;

Here's the sketch I did with my bamboo pens and colored ink.