Oil pump worm gear hex size

I can't get my oil pump worm gear off. I know it is LH thread and have read a number of comments to just crank harder or use heat (neither has worked yet). Can somebody confirm the hex size on the nut? I've been using a 15/16 wrench on it because that is what I have, but I rounded a corner on the nut and I'm thinking it might be 1/2W. Does anybody know for sure?

You are asking about the hex on the end of the 06-7889 worm, correct? Are you using a 6-point socket? My 6-point Whitworth socket labeled "9/16BS 1/2W" fits it best.
Bill

Thanks pantah, yes that is the part I'm talking about. I'm ordering a 1/2W socket tonight - that will also be much easier to put an extension onto for more leverage.