John is right on the money. The amount of radius needed to prevent any stress risers is extremely small. If you use the end of a a round needle file, and just break the sharp edge, right at each corner where the tang joins the blade....thats all you need.
I think one of the best tools ever invented is a carbide "file guide". I just get the shoulders "close" before heat treat, then after heat treat, using that carbide file guide, a couple of quick "zips" on the grinder and things are done.
Thanks gents for the file guide talk. Ed thanks!
I do still make the file guides but try to make knives too. I,ve spent over 3 months on this one dagger so a few file guides is a pleasant change of pace.