Ken, you don't have to turn the delrin. You buy it the size you want, I generally use 5/16" delrin rod to make the tenon. I cut the stock delrin to the length I want to use and hold it in a Nova scrolling chuck with a set of pen turning jaws. I face it with an appropriate end mill, generally a 3/8" works fine. I don't use a Forstner bit, IMHO they are too wobbly. Then I use a starter bit to drill into the delrin. I then drill through the delrin I have chucked with my 5/32" airhole bit. I then face it again.
I then flip the piece of delrin around in the pen jaws and pass my airhole bit through from that end.
Then I face it with the end mill and my tenon is done. I rough up the end I will insert and glue into the mortise hole (I also rough that up) I drilled in my rod stock or pre-formed vulcanite stem with 5 minute epoxy.
I forgot to mention that when I use pre-formed vulcanite stems I always cut the cast tenon off. I don't turn it because I don't have a metal lathe for that kind of fine work. My hands are too shaky.
I also face the rod stock or pre-cast vulcanite with both an end mill and my scraper. I then check it and if necessary use a bit of sand paper on the faced end.
Make sense?
I can take some pictures for clarity if you like.
Anyway, that's the way I do it for now.
