I decided to put my milling machine through its paces this afternoon and came a way with a nice cutaway of the master lock combo lock key override cylinder (it was all I had on hand, making this more of a practice).
Here are a few pics
I would like to do this on a full deadbolt cylinder so could anyone recommend a brand with a similar style removable cylinder (preferably cheap

). I bought a kwikset this afternoon but it was more of a one piece design and lends itself poorly to this project.