The plans for this conversion have been posted at sheldonbrown.com for many years. Ever since I first stumbled across the page I wanted to try the conversion for myself. Fast forward a few years and I finally have the equipment to make it possible.
A groove must be machined in the planet cage, seen on the left. The left hand ball cup must be knocked out of the hub shell and have a matching groove machined into it. A bar with a hole in it must also be fabricated, to lock the ball cup and the planet cage together.
The internals are hardened, and by golly are they hard. My end mill didn't stand a chance. A hand file couldn't even put a scratch in it. So with my torch I spot annealed the areas that needed to be machined. I heated up the areas to red and tried to hold that temperature for a little bit, then let it cool slowly. And it actually worked!!!
Here is the hub reassembled (except for the ball bearings and cone).
Got it all done in time for the Philly Bike Expo, for the presentation on Sturmey Archer hubs, put on by Trophy Bikes. Have not yet heard how the presentation went, maybe I will get some pictures in a day or 2.