I've been making pens for over a year now, and I made about 400 of them using CA glue for adhering the tubes inside the wood (and acrylic) blanks. I always had a problem with acrylics though, because every so often, the tube would detach from the acylic while I was turning it. I'd have to stop, take it off, reglue it, and even then I'd always wonder if it will do that down the road while someone is using it.
The reason I like CA glue was because, like most reasons other like it, it's fast. It dries very quickly and you can get right to the part we all love the most: the turning. Well, I finally got sick of gluing my fingers together, having tubes get stuck halfway into oily woods like cocobolo and ebony, and having the acrylics come apart. So I decided to take the "test of patience" and use two-part epoxy.
I've made about 100 pens now since I've been using epoxy and I will never go back. The epoxy is great for adhering dissimilar materials like metal and plastic (acrylics), and with burl woods and things with inconsistent grain and holes, it does wonders with stablilizing the wood and filling gaps. I use Loc-Tite 5-minute 50/50 two-part epoxy in 4 oz. containers. That much glue will last about 200-300 pens.
The epoxy takes a bit of patience....about 30-40 minutes to cure, but it's completely worth it by the workability of it, the longer open time, and the fact you won't glue your fingers together and then have to wait days for the glue to peel off of your skin. Try epoxy!!!!