I do machining and when I got my tandy lacemaker I had that same thought to, the problem that I ran into wasn't so much in how to machine the body of the lacemaker, but rather how to put the really thin slot in it for the blade. I ended up designing some lace making tools of my own, which I had planned to make and sell, but as of yet haven't done so. Maybe I need to get back on that project. The simple little lace maker design that I came up with would cut the lace, thin the lace, and bevel the lace, and was only about 1" wide and about 5" long and about 3/4" thick if I remember right.
Chris