The end of the hub at the flange face or the end of the hub at the free end of the flange. Normally the large end and small end but in the case I'm looking at the hub is straight, not tapered.
Thanks. I found my answer finally. Sketch (3) does not call out the radius specifically but Note 2 says to refer to Sketch (2) for dimensions not shown. This leads to Note 3 which states that "r to be at least 0.25g1 but not less than 3/16 in."