Use a cobalt drill bit that is slightly larger than the hole that the ball rests in.
You need to drill out all of the material of the ball so it won't catch on the walls of the hole.
The metal is harder than average, and a cobalt drill bit will do the trick.
BTDT.

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022