Looks like weld failed. If the arm goes back into the holder, you could try JB Weld metal epoxy. Check online pic for the correct position regarding the tension screws and arm direction. Clean rust off and give it a try.

If I'm not mistaken, and some of you machinist types check me on this, but I believe that was a press fit where the hex shape of the arm is slightly larger than the hex receiving hole in the ball of the ball and socket joint. The two were put together using a press. My guess is that it might not be reliable any longer, though I haven't any idea how strong the JB Weld epoxy might be. However, if it were to fail, it could damage the tom quite a bit falling from that height. Might be better off looking for a replacement or at least a new ball and arm piece from an arm that is toast on the bottom.

They do come apart. There is a small drift pin in the outer/lower portion of the socket. Drive that out with a small drift and you can unscrew the top of the socket and remove the ball.

Yes, it does look like the hex section was originally "pressed" into the ball section. The other arm I have looks like one solid piece with the chrome plating covering both pieces, which fills in the seam between the two pieces.

The JB Weld option might work, but I agree it might be to risky. I think there might be a way to sleeve the hex rod. Right now the hex rod has a lot of play when inserted into the ball section. I have a friend that is a metal worker, so I'll ask their opinion. The ball is drilled straight through, so I could remove it , insert the hex rod and weld from the bottom.

-Tim

They can be fixed! what you need to do is remove ball from mount and have it re welded by an experienced welder. The way that l arm is made is a two piece the l arm and the ball if you weld it correctly it as good as new.