The part I did tonight was to cut the dovetail. It is a 60 degree dovetail to fit my quick change tool post. This was the first time I have cut steel on my mill so it was a learning experience. Main part was getting the speed right for the material. It seemed to work better with a faster cutting speed than I expected. I thought I was going to cut a groove to depth and then work to the side to width. Wrong answer. I needed to cut down on both parts I milled out before switching to the dovetail cutter.
The next part will be to cut the step on the side to support the cutter holder and then it will just be drilling for the depth adjuster and a key to stabilize it.
Here it is sitting on the toolpost. I am really pleased that it came out as well as it did.
Part of why I am taking so long on my build for my router is to learn machining as I go. This won't be part of the router but it will make it a lot easier to cut threads to make some of my own parts for the motion components.
Here is a video from Bogstandard on madmodder.net (<- a link to the forum discussion) that is the design that I am basing mine on. Don't expect me to make one as nice as his.