Well, I didn't intend this post to get out of hand, only wanted to offer my services if so desired at a Cubfest. Really too involved for me to try to explain here. Sometimes it is necessary to use a big sledge and pipe to break them loose, Al, driving the hub away from the taper. (In addition to the key extractors in my attachment, following.) These are not as simple as appears, they are a compound taper, which holds them into the slot between the head of the key and the hub. I've actually seen these made in our factory, next to the combine assembly line. They used to be hardened by hand, but now is automated, as is the cutting and plating process.
The curved one removes the keys from an inset (dished) hub. Yes, there are some instances where it has been necessary to drill out the key, but if "fitted" correctly and not distorted by a BFH, they normally come out. Then again, I've not had to remove any that are more than 60 years old, either.
We sell around 200 extractors a year thru our dealer network, and are used on balers, forage harvesters, and combines. (yes, built in 2012)
I did not intend this as a sales pitch either, so take it as it is..
I hope this helps in some small way. (that was my only intention) Regards, Stan