Well, I didn't get a chance to go to the new machine shop yesterday, but from what I understand they first bore a small hole the size of the bottom of the tapered square and then use a machine that is called a EDM. It burns out the rest of the metal with an electrode the shape of the taper, while the stock is in a tank of some type of oil. I haven't seen it done, yet.
But I will be going there either Friday or Monday morning to start talks with them.
I was cautioned that this could be an expensive process to do....
We'll have to see....