I think I can safely say that for most of us, stem making is the least favorite part of fabricating a pipe. Cutting the frigging slot and forming the funnel evokes all the rotten language I learned in the Navy. Way too much time spent on it (for me anyway). I'm sure there are those out there that can do it with their eyes shut. To ease my own frustrations I put together a rig to cut the slot and form the funnel in one shot. I made the first test this afternoon and it works like a champ. The only tweaking needed is shortening the shank on the cutter. Once cut, the only thing left to do is blend the funnel to the airway and do a little very minor file work and polish the innards. The concept is not my original idea. I saw one on the web that some European makers had put together out of wood.
The tip of the end mill sits at the pivot point of the motor holder that swings back and forth so as to prevent wallowing out the airway. The rod holder moves up and down on fine thread to accommodate different diameters and to aid in getting the slot centered. There is ample movement in the axis of the airway combined with the swing to make about any width and depth of slot one could need.
At any rate, I'm looking forward to putting it to good use.
Chas.
Of course if he could crop out creating the 
