I drill a hole the diameter of the tool I want to use in the end of the bar, and hold it with a set screw on the side. I had machine shop's do the work, but I was told the metal is not that hard. You could probably do it yourself with a big drill press and some new bits. I have found I like two presses, one for holes, and another for rivets/snaps. Nice part is, no die's needed, you can set snaps and rivets all day long with cheap hammer tools. You'll have to rig some sort of deck for the arbor press, but it's not that big a deal. Metal's nice, but oak is pretty strong, and you dont need a machinest. I use harbor freight presses, and sent them to the powdercoaters. Have done several, they work great.
They come in two sizes. If you have the room to leave it in one place, the big one is nice. If you are going to move it around, get the smaller one.