I've had a Bridgeport slotter on the back of my bridgy mill for years. Seldom used but very handy when needed. Alas, I sold this mill and have no way to mount it anymore. I'm wondering about a replacement machine. The shapers I've seen don't look too handy because most of my use is for inside splines and slots. A rotary table and vise don't look easy on a shaper.
I came across this:
Karl