Do you have a pic of the head. Showing where the top radius cut goes ?
With a bore head it will be hard to set dia of radius. I would take a 5 inch disk of stock about 1/2 inch thick and center it on mill. Then drill and bore a 3/4 bore on center then move off center half of radius dia and then drill and bore or ream dia of needed radius. Then use a 3/4 piece of stock inserted into disk as a shank to hold in collet in mill. Then insert a round piece of carbide into disk. You would have to grind
Needed radius on end of carbide.
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The easiest way i found to solve this issue if you dont have a resizing app on a smartphone is to simply open the picture on your phone and take a "Screen Shot" of the picture in question and then post the screen shot duplicate. The default setting on my screen shot is small enough to post here without a problem without messing with my camera's settings.Having trouble posting pics... File too large