I'm putting in a new axle but I need to get the old one out, how do you get the disk break HUB off of the old one?

 

Take the axle nut off and the right hub, it slides right off the right side. It sits on splines, held in place by the pressure from the axle nut.

 

Sandneck I did that, but how do you get it off of the splines?

 

Don't hate me for saying this...........
You might have to use a torch. I have seen a few that have never been off and , well, um , its not pretty. Usually the lock nut will be seized if the hub is, but sounds like you got that off. The only advice I can give you is to us heat, WD-40, and pound the hell out of it. The last one we did, ended up with a aftermarket anti-fade, and brake hub. We had 1/2 the axle in a 20ton press and that damn thing would not budge. That cost a new axle, and everything....
GOOD LUCK!