I put balls from the craft store on the end of EMT for some shop-made tool
handles. I drilled and tapped the balls for 3/8 coarse bolt thread. A 3/8
bolt head will jam into 1/2 EMT conduit, which I then brazed. Then you
just screw the ball onto the end of the shaft. I didn't use any glue.

You need at least a drill press, or better a lathe, to drill a sphere
straight and true.

If you were to drill a larger hole to receive the whole EMT tube into the
ball, you'd weaken the ball.