External oil groove? Today that would be done on a CNC machine with a rotary fixture also being controlled.
You can do almost as nice a job with your Bridgeport, a ball endmill, and a dividing head. (Or as perfect a job with change gears added in linking table travel and dividing head rotation) Forget about the change gears as you probably don't have them...
Back to the basics I'd probably stop short of figuring out the math for table position and angular rotation at regular steps. (Though not confusing if you want to)
Instead draw your pattern on there with a sharpie, possibly transferred from a paper template traced from the original. Then manually follow along both rotation and table travel. I'd cut it full depth in one pass so you don't have to trace more than once.
That would be a step between full CNC or fully geared manual setup and hand held dremel.
Grigg
