The ballmount that James recommends is made of two stamped SS semi-hemispherical pieces. In between these halves is ferrule which the cross bolt goes through. It is designed for light mobile antennas like those used for CB. When used with heavy antennas like a Tarheel or HiQ, it is necessary to tighten the center bolt beyond what the split ferrule will withstand. Sooner or later (usually sooner) the ferrule bulges thus loosening the ball and your antenna finds itself laying on the ground!
No one, and I mean no one, makes a decent ballmount any more. GE is long since gone, but if you can find one of their old Master mounts, you're in luck as it will hold just about any antenna you can screw into it.
For more information of the GE mount, visit my web page under 'ballmount envy'.