Hi. I am also interested in where I can get more information about your project, such as the source code and the spindle encoder arrangements. I assume that you also need to generate a synch/registration pulse once for each revolution of the lathe spindle.
I have just fitted a stepper to the lead screw on my 95 year old lathe and was now going over the possible ways to drive it when I found your post. I like what you have done as it was generally the sort of solution I was considering using an Arduino. I didn't want to have to use a PC and Mach3 (or the Linux equivalent). If the additional information is on the German CNC website then I am in trouble as my German language skills are non existent.
Would appreciate whatever guidance you can give.