I have no doubt Randall is right but since you brought up the subject, I don't think it is considered ideal but is often done to parts that are hard to find replacements for. I had it done on my Healey 100 head, which have been described as having two stages in their lives, cracked, or about to crack. This was a few years back when machine shops were a little more common. I assume there is a bit of skill or art involved, because my guy and a couple other gearheads said there was only one guy that could do it, and he was a bit of a magician.
He did do it for me, I asked if it would hold, he said he wouldn't do it if it wasn't going to be as good as new, I only kept the car a couple years after but nothing blew up.