I know this really is helpful only to those who have a bandsaw and milling machine. But maybe the fixture idea is useful in other ways.
This is a simple fixture, a flat sturdy plate with a threaded shaft collar screwed to it. Yes, it's an off-the-shelf item, available in many thread configurations, both National Coarse and Fine, from McMaster-Carr or MSC. I like the two-piece split collar better than the one piece style collar illustrated, because it accommodates variations in plug size better.
Screw the already threaded plug into the fixture. Clamp in saw, tilted to get the angle you need for the flare of the tang. In this pic, the sides have already been slabbed off, and the underside of the tang is being cut.
Flip the plate vertical in the saw, and make a cut to meet the first cut.
With this style fixture, the part can be rotated to match the angle of the blade. The saw is only parallel to the base when the saw is all the way down, so rotate the part accordingly.
Tang is only sawed at this point. Now take it to the mill.
Mill all sides, rotating part in fixture as needed. Because the part is so extended, take light cuts only.
