Mill vise cut ball bearing for the sliding jaw ?

[Chipper5783]

Sloth2009 did a great job showing us his "screwy ball".

Been busy for a few weeks and haven't done much milling. Today I made a "screwy ball" out of a 1" ball bearing. I saw a few videos online where people used them to help hold non-square workpieces up against the fixed jaw. I just got this little machinist vise and used it and some nuts for the setup. I ground a flat in the ball with my belt sander to save some time and then made some passes with my carbide face mill. It turned out pretty nice.
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That got me thinking about what size ball to use. I suppose one would use what ever size they can track down. Obviously it shouldn't be too small. Is bigger better?

I came across a 6" ball (from a ball valve) that could be cut to provide a larger radius push pad (though not as hard as the ball bearing). Would it be worth the effort? Would it work any better?

 

[aliva]

Looks kind large for everyday use I ground a flat on ball from a 4 bearing seems be about the right size for most situations.
I have balls from bearings 1/2" and 3/4"