Thanks for the info by machine work to you mean cut and grove or notch it or make splines so the joint can grip the smooth round steering shaft?
Correct, and as mentioned the simplest method is to use a u-joint with what they call a double D end on it, then you simply take the 3/4 shaft and mill flats on opposite sides so it fits, easy to do in the (milling machine) vice and about a 1/2" end mill, just bump both sides in the same setup, and the radius of the mill makes a nice transition back to round.
Grigg
