I just finished up my first set of arrows with self nocks. I still have a bit of a learning curve trying to cut them in neatly. Oh, well, they may be uglier than a mud fence, but they shoot pretty well.

I have an English style longbow made by a friend. I wanted some appropriate arrows, so I decided to make up a batch. Despite watching a bunch of videos, I have not yet gotten the knack of it. No problem, I'll just start on another dozen and see if it gets any better. Maybe before long I will make a set worthy of a pic. At least the blue silk thread I used to wrap them is pretty.

Try a band saw to get a kerf going to help guide the final cut.  Get it as close to center as you can then just spin the shaft 180 degrees and cut again.  The kerf should help you keep things lined up.

Gringol, I don't have access to a band saw, so I have been using a hacksaw for the entire cut. Then using a file to widen it. I have difficulty making a good straight cut.

Make yourself a jig that you can slip over the top of the shaft that will guide your cut.  Just drill an appropriate diameter hole in a hardwood block and cut a slot in it.  That slot has to be accurate, of course.  Maybe you could gain access to a table saw or band saw for that cut.  Once it's done, you should be able to make all of your cuts perfectly.  I think 3 Rivers sells a jig for doing this if you don't want to make your own. Good luck.

Tape 2 or 3 hacksaw blades together to get a uniform width of cut.  Might help a little

They make a self nock jig, I have had one, it comes with a round hack saw blade....
   Sorry can't remember where I got it....